X-ray Microanalysis of Elements in the Masticatory Muscle after Paresis of the Right Masseter

Muscle activity and function appear to be related to ionic concentrations in the muscle. We investigated whether muscle paresis induced by injection of Botulinum toxin A (Botox) in 16-week-old pigs over a 56-day period is associated with ionic changes in the affected muscles. Tissue samples were taken from the masseter, temporalis, medial pterygoid, and geniohyoid muscles by a standardized method and used for energy-dispersive x-ray microanalysis in an environmental scanning electron microscope. The largest increase in Na+ was measured in the right and left sides of the masseter muscle in treated animals. Additionally, a significant elevation of Na+ was measured in the anterior part of the temporalis muscle and in the pterygoid muscle (P < 0.05). In temporalis and pterygoid muscles, an increase in sulfur in both sides of treated pigs’ heads was observed. Botox® has an indirect impact on ion concentrations, resulting in changes in muscle functional capacity and adaptive compensation of paretic muscle function by other muscles.

DG3173 (somatoprim), a unique somatostatin receptor subtypes 2-, 4- and 5-selective analogue, effectively reduces GH secretion in human GH-secreting pituitary adenomas even in Octreotide non-responsive tumours

OBJECTIVE

Somatostatin analogues (SSA) reduce autonomous GH secretion by activating somatostatin receptors (sst) 2 and 5 in 50-60% of acromegalic patients. However, by inhibiting insulin secretion these SSA reduce glucose tolerance. DG3173 is a novel SSA with additional binding to sst4 and low insulin-suppressing activity. We investigated the effect of DG3173, including its relation to specific tumour characteristics, on GH secretion in human somatotroph adenoma cell cultures (hSA) in comparison with Octreotide.

METHODS

Twenty-seven hSA were characterised immunohistochemically for their hormone- and sst-expression, granularity and pre-surgical therapy with SSA. GH was determined in supernatants of hSA treated with DG3173 or Octreotide in time- (n=6) and dose-response (n=21) experiments. A positive response was defined as GH suppression to below 80% of baseline.

RESULTS

In the dose-response experiments DG3173 suppressed GH secretion in more adenomas than Octreotide (10/21 vs 5/21), including 38% (6/16) of Octreotide non-responders. In responders the extent of GH suppression and IC(50) were comparable for both SSA. The response-rate of both SSA was higher in monohormonal vs bihormonal adenomas, yet GH declined similarly in both groups. Neither pre-surgical SSA (n=6) nor tumour morphology was related to the GH response. However, semi-quantitative analysis indicated a small but significant negative correlation between the GH response to Octreotide and the immunoreactivity scores of sst2 expression.

CONCLUSIONS

DG3173 equalled Octreotide in suppressing GH secretion in hSA. Since DG3173 suppressed GH in some Octreotide-non-responsive adenomas, its clinical effectiveness will be worth testing. Moreover, its reduced insulin-suppressive potency would make it a valuable alternative to Octreotide.

Efforts to establish an animal model of Fanconi syndrome after ifosfamide administration to rats

About 10% of children develop Fanconi syndrome (FS) a few months after ifosfamide (IFO) treatment. To establish an animal model, IFO was injected as 4 or 5 treatment courses (TCs, once daily for 3 consecutive days), to adult female rats (AF, 8 mg 100 g(-1) body wt, 4 TCs), to young female rats (YF, 8 mg 100 g(-1) body wt, 5 TCs) and to male rats (M, 6 mg 100 g(-1) body wt, 4 TCs). In the adult female rats, polyuria with electrolyte and albumin wasting occurred acutely, 2 days after the first treatment course. After the third treatment course, 30% of the rats died, but survivors showed a reduced excretion of electrolytes and glucose. The body weight increase was significantly diminished in adult female and male rats by about 25% or 70%, respectively. Up to 5 months after 5 TCs in young female rats, 15% of the animals died but the survivors did not show any sign of renal failure. In males, 28% of the rats died and in surviving animals the excretion of electrolytes, proteins and glucose as well as GFR were reduced 7 weeks after the last treatment course. There were no pathomorphological changes in kidney and liver. Determination of renal and hepatic cytochrome P450 activities indicated that results of adult female and male rats could be caused by starving, known as a common side effect of IFO, and not by its nephrotoxicity. Altogether, it was not possible to establish a model of a Fanconi syndrome persisting after cessation of IFO treatment in our rat strain, whereas acute, FS-like IFO effects on the kidney could be shown.

In vitro investigations on the differential pro-oxidant and/or antioxidant properties of cyclosporin A and tacrolimus in human and rat liver microsomes

OBJECTIVE

The use of cyclosporin A (CSA) and tacrolimus (TAC) in organ transplantation and in the therapy of immune disorders is often hampered by adverse effects, mainly nephro-, hepato- and neurotoxicity. For the development of these side effects, among others, an increased formation of reactive oxygen species, probably generated by the cytochrome P450 (CYP) system, has been accused. Since in this respect literature data are inconsistent, in the present study possible pro- and/or antioxidant effects of CSA and TAC and the involvement of the CYP system were re-evaluated in vitro.

METHODS

Effects of CSA and TAC were examined on CYP mediated oxidase functions by stimulated lipid peroxidation (LPO), H2O2 production, and lucigenin (LC) or luminol (LM) amplified chemiluminescence (CL) in liver microsomes of either untreated rats or of rats treated with beta-naphthoflavone (BNF), phenobarbital (PB) or dexamethasone (DEX) and in human liver microsomes.

RESULTS

In rat liver microsomes, CSA displayed pro-oxidant properties (though only very slightly), whereas in human liver microsomes small antioxidant effects were seen. With TAC in both species the antioxidant capacity prevailed. Treatment of rats with BNF or DEX caused an increase in the pro-oxidant effects of CSA with respect to LPO or LM-CL, whereas in liver microsomes of DEX-treated rats H2O2 production and LC-CL were diminished.

CONCLUSIONS

CSA seems to have both pro-oxidant and antioxidant properties, whereas with TAC mainly an antioxidant capacity was seen. The CYP system seems to be involved in the pro-oxidant influence of CSA. Whether pro-oxidant or antioxidant effects predominate may depend on the antioxidant capacity of a tissue and on the CYP isoforms mainly present.

Cryopreserved precision-cut rat liver slices: morphology and cytochrome P450 isoforms expression after prolonged incubation

Precision-cut liver slices are an accepted in vitro system for toxicological investigations. However, cryopreservation of slices would make a more efficient utilisation, particularly of human liver tissue possible. In the present study sections of cryopreserved male rat liver slices were examined immunohistochemically for cytochrome P450 (CYP) isoforms expression after prolonged incubation and after exposure to typical inducers. Morphologically, with just thawed slices no major alterations were seen, but remarkable cell damage was observed even after 2 h of incubation mainly in the middle of the slices and in the periportal and intermediate regions of the lobules. After 24 h of incubation, viable cells were only observed at the edges of the slices or around bigger vessels. In the viable cells of the cryopreserved liver slices after 2 h of incubation CYP expression pattern was similar to that in normal liver specimens: a low CYP1A1, but a strong CYP2B1 and 3A2 expression predominantly in the central and intermediate lobular zones. After 24 h, the immunostaining for CYP2B1 and 3A2 in the viable cells was reduced, but that for CYP1A1 was increased. Incubation with beta-naphthoflavone further elevated CYP1A1 and 2B1 expression. Phenobarbital caused an enhanced CYP2B1 and 3A2 and dexamethasone and pregnenolone 16 alpha-carbonitrile an increased CYP3A2 immunostaining. These results show that also in cryopreserved liver slices and after a prolonged incubation, a distinct expression pattern and an in vitro induction of phase I enzymes can be demonstrated immunohistochemically.

Influence of the sagittal advancement of mandibulae on myofibrillar ATPase activity and myosin heavy chain content in the masticatory muscles of pigs

Endurance muscle stress leads to polymorphic expression of myosin heavy chains (MyHC). Histochemical and electrophoretic analyses were performed on different masticatory muscles (masseter, temporal, geniohyoid and medial pterygoid) of 10 weeks old pigs after 28 days of chronic sagittal advancement of the mandibulae. The differentiation between fiber types was investigated histochemically with the myofibrillar ATPase (mATPase) method and by immunohistochemistry. Expression of different MyHC isoforms was also assessed by means of immunoblotting with monoclonal antibodies. The results of both methods were compared. Chronic sagittal advancement of the mandibulae led to an increase in the cross-sectional area of type I fibers and type I MyHC in the anterior part of the masseter, the distal part of the temporal and the medial pterygoid muscle. In the present study, clear differentiation between type I and type II muscle fibers in all histological analyses was possible. However, mATPase classification of subtypes of type II fibers may lead to misinterpretations. Additionally, a direct correlation between the type I MyHC concentration and the type I fibers was seen in enzyme histochemical and immunohistochemical staining. The defined cross section of fibers is important for the histological investigation in small muscles. The immunoblot method seems to be more sensitive and less subjective for measurement of muscle changes. It can be concluded that the immunoblot method used for measuring the MyHC content is a valid alternative for fiber typing in small muscles as it is less time-consuming and more sensitive than qualitative histochemistry.

In vitro induction of cytochrome P450 2B1- and 3A1-mRNA and enzyme immunostaining in cryopreserved precision-cut rat liver slices

With the exception of cytochrome P450 (CYP) 1A1 and its mRNA, in vitro induction of other CYP forms has not been demonstrated in cryopreserved liver slices until now. Therefore precision-cut rat liver slices were cultured after cryopreservation and thawing in William's medium E for up to 24 h in the presence of inducers to demonstrate CYP2B1- and CYP3A1-mRNA induction. CYP-mRNA expression was determined by competitive RT-PCR. Exposure to 100 microM phenobarbital caused a more than 20-fold increase in CYP2B1-mRNA expression within 24 h, reaching concentrations comparable with those of PB-exposed fresh rat liver slices. Exposure to 1 microM pregnenolone 16 alpha-carbonitrile enhanced CYP3A1-mRNA expression by more than 30-fold within 24 h. This is in the same range, although with higher variability, as detected with fresh liver slices. In spite of considerable variability among the thawed slices, the induction factors are high enough for a sensitive detection of an induction at mRNA level. Additionally, immunostaining of respective CYP-forms was performed in sections of few samples, indicating CYP increase in viable cells of cryopreserved slices.

Estradiol, testosterone, dehydroepiandrosterone and androstenedione: novel derivatives and enantiomers. Interactions with rat liver microsomal cytochrome P450 and antioxidant/radical scavenger activities in vitro

Interactions of 27 steroids, among them 17 derivatives such as ethers, sulfates and amidosulfonates derived from 17 beta- and 17 alpha-estradiol, from testosterone and alpha- and beta-dihydrotesosterone and from dehydroepiandrosterone with rat liver microsomal cytochromes P450 (P450) were investigated in vitro by assessing binding to P450 and effects on P450 mediated monooxygenase functions as measured by different model reactions: ethoxyresorufin O-deethylation (EROD), ethoxycoumarin O-deethylation (ECOD) and ethylmorphine N-demethylation (EMND). With the exception of 17 alpha-estradiol-3-dimethylamidosulfonate, estrone, its -3-methylether and -3-amidosulfonate and testosterone, all other steroids displayed type I or reverse type I binding to P450. All steroids inhibited EROD activity in micromolar concentrations. An additional strong inhibition of ECOD and EMND activities was only demonstrated for the androgens and progestins. Estriol, estrone and mestranol displayed less inhibitory actions on the model reactions than estradiol. No major differences in comparison to the parent compounds were noted with the other derivatives. The only exceptions were 17 beta-(8,9-dehydro-14 alpha,15 alpha-methylene)estradiol, which displayed stronger effects than estradiol, and dehydroepiandrosterone-3-sulfate, which was less effective than dehydroepiandrosterone. Possible antioxidant properties of the steroids were examined by the stimulated lipid peroxidation (LPO), H2O2 production, and lucigenin (LC) and luminol (LM) amplified chemiluminescence (CL) using rat liver microsomes. Additionally, the influence on rat whole blood chemiluminescence (WB-CL) was assessed. All the estrogens, but not their methylethers and amidosulfonates inhibited LPO in micromolar concentrations. The effects on the other oxidase model reactions or on WB-CL were less distinct. Only ethinylestradiol and 17 beta-(8,9-dehydro-14 alpha,15 alpha-methylene)estradiol displayed a strong inhibitory action on all model reactions. With the exception of dehydroepiandrosterone-3-sulfate, which in general had only weak effects, the androgen and progestin derivatives, in contrast, strongly decreased H2O2 formation and LM- and LC-CL, but were mostly ineffective on LPO and WB-CL.

Temporary warm ischaemia, 5/6 nephrectomy and single uranyl nitrate administration--comparison of three models intended to cause renal fibrosis in rats

In patients the progression of pathologic renal processes after the treatment of primary disease is a problem of increasing importance and therapeutic strategies are insufficient till now. The aim of this paper was to search for rat models of interstitial fibrosis as a basis for testing therapeutic strategies to prevent end-stage renal failure. Experiments were done on adult female Wistar rats (Han:Wist) to investigate long-term consequences of temporary warm ischaemia, 5/6 nephrectomy (5/6 NX) and single uranyl nitrate (UN) administration (0.3 or 0.5 mg/ 100 g body wt. intraperitoneally). Observation time was 20 weeks after injury in each group. Creatinine clearance, urinary protein excretion and hydroxy-proline (OH-proline) concentration in renal tissue were measured and light microscopic investigations were done to characterise both quality and time course of long-term renal damage in relation to matched control animals. Temporary warm ischaemia and 5/6 NX did not cause any fibrotic changes during the 20 weeks observation period. The higher UN dose led to decreased creatinine clearance, increased urinary protein excretion and enhanced OH-proline concentration in renal tissue. Morphologic investigations showed fibrotic areas containing strongly dilated and atrophic tubules with thickened basal membranes. These effects can be seen from week four after UN administration up to the end of the observation period. In conclusion, administration of one single dose of UN is a simple procedure to induce interstitial renal fibrosis as an experimental model to investigate therapeutic strategies for their prevention.

Morphology and cytochrome P450 isoforms expression in precision-cut rat liver slices

Precision-cut liver slices are a widely accepted in vitro system for the examination of drug metabolism, enzyme induction, or hepatotoxic effects of xenobiotics. The maintenance of the distinct lobular expression and induction pattern of phase I biotransformation enzymes, however, has not been examined systematically so far. Thus, in the present study, both longitudinal and transversal sections of male rat liver slices were investigated morphologically, as well as immunohistochemically for the expression of different cytochrome P450 (CYP) isoforms after prolonged incubation or after exposure to typical inducers. Histopathological examinations revealed an increasing vacuolization of the periportal hepatocytes mainly in the middle of the slices from 6 h of incubation on, paralleled by a loss of glycogen in the respective cells. After 24 h, mainly in the center of the slices, necroses of cells occurred. After 48 h of incubation, typically a central band of coagulative necrosis flanked by superficial layers of viable cells was observed. Freshly prepared slices displayed a CYP subtypes expression as normal liver specimen, a very low centrilobular CYP 1A1 immunostaining, but a strong CYP 2B1 and 3A2 expression predominantly in the central and intermediate lobular zones. From 2 h on, the immunostaining for CYP 2B1 and 3A2 was to some extent reduced. After 24 h of incubation with beta-naphthoflavone, the CYP 1A1 and 2B1 expression was induced mainly in the viable cells around central veins, around some portal fields with bigger vessels and in the cell layers close to the slice surface. At the same sites, phenobarbital led to an increased CYP 2B1 and 3A2 expression and dexamethasone to an elevated CYP 3A2 immunostaining. These results show, that an in vitro induction of phase I enzymes in precision-cut liver slices can be demonstrated also immunohistochemically.

Transplantation of fetal liver tissue suspension into the spleens of adult syngenic rats: effects of different cytotoxins on cytochrome P450 mediated monooxygenase functions and on oxidative state

Syngenic fetal liver tissue suspensions were transplanted into the spleens of adult male Fisher 344 inbred rats. Four months after surgery, transplant recipients and age matched control rats were treated with different cytotoxins (allyl alcohol [AAL], bromobenzene [BBZ], carbon tetrachloride [CCl4], or thioacetamide [TAA]) or the respective solvents 24 or 48 hours before sacrifice. Effects of the cytotoxins on P450 mediated monooxygenase functions in liver and spleen 9,000 g supernatants were assessed by measuring the model reactions ethoxyresorufin O-deethylation (EROD), ethoxycoumarin O-deethylation (ECOD), pentoxyresorufin O-depentylation (PROD), and ethylmorphine N-demethylation (EMND). Additionally, the influence on the oxidative state was investigated by assessing the liver and spleen tissue content of lipid peroxidation (LPO) products and of reduced and oxidized glutathione (GSH;GSSG). The livers of both solvent treated transplant recipients and control rats displayed regular EROD, ECOD, PROD and EMND activities. After AAL treatment EROD and EMND activities within the livers were not affected, but ECOD and PROD activities were increased. BBZ administration caused a decrease in EROD and EMND activities, ECOD activity remained unaffected, and PROD activity was even increased. CCl4 and TAA administration caused a strong reduction in the activity of all four model reactions. Spleens of control rats displayed almost no P450 mediated monooxygenase functions, independent whether the rats had been treated with the cytotoxins or not. In the transplant containing spleens, however, significant EROD and ECOD, but hardly any PROD or EMND activities were seen. After AAL administration EROD activity was not affected in the transplant containing spleens, but ECOD activity was increased. BBZ treatment led to a decrease in EROD and an elevation in ECOD activity. CCl4 and TAA strongly reduced the activity of both of these model reactions. The tissue content of LPO products within livers and transplant containing spleens was significantly increased after BBZ and CCl4 treatment. An elevation in LPO products was also seen in the spleens of the control rats due to CCl4 administration. Tissue GSH and GSSG content in both livers and transplant containing spleens were strongly reduced after BBZ treatment. After CCl4 administration only a significant decrease in liver GSSG contents was seen. TAA treatment caused a reduction in the GSH and GSSG content in the spleens of both transplant recipients and control rats, but not in the livers. From these results it can be concluded, that the effects of cytotoxins like AAL, BBZ, CCl4 or TAA on P450 dependent monooxygenase functions and on oxidative state are exerted in the ectopic intrasplenic liver cell transplants in a similar way as in normal orthotopic liver.

Cytochrome P450 (P450) isoforms expression, P450 concentration, monooxygenase activities, reactive oxygen species formation, lipid peroxidation, and glutathione content in wild catch carp and tench liver--influence of a two weeks exposure to phenobarbital

Carps, both sexes, 3 years old, weighing about 1 kg, and tenches of both sexes, 6 years old, weight about 250 g, were caught from a Thuringian lake without industrial pollution in November 1995 (fish without food uptake, water temperature at about 10 degrees C) and kept for 2 weeks in basins with clean water and addition of 0, 0.1, 1.0 or 10.0 mg/l phenobarbital-Na (PB). The concentration of PB was controlled during and at the end of the exposure period. The animals were fed pellets, but no food uptake was observed. After 24-48 h in fresh water the fish were sacrificed and the following hepatic parameters were immediately determined biochemically: monooxygenase functions: cytochrome P450 (P450) content, ethylmorphine N-demethylation (EN), ethoxycoumarin O-deethylation (ECOD), ethoxyresorufin O-deethylation (EROD), 7-benzyloxy-4-methyl-coumarin O-debenzylation (BCDB); oxidase function indicators: microsomal Fe2+/NADPH dependent hydrogen peroxide formation (H2O2), microsomal Fe2+/NADPH dependent luminol and lucigenin amplified chemiluminescence (LMCL, LCCL), microsomal Fe2+/NADPH dependent lipid peroxide formation (LPO); oxidative state: lipid peroxidation products (TBARS) and GSH and GSSG. Additionally, the expression of three P450 isoforms, 1A1, 2B and 3A, was assessed immunohistochemically in tissue samples from brain, gill, heart, spleen, liver, gut and ovary of both fish species and in kidney of tenches. PB did not influence body or liver weights, but increased liver P450 concentration in both species by 50-100%, though not significantly. Carp: PB increased both EN and EROD significantly, but not ECOD and BCDB; H2O2 and TBARS were enhanced significantly. LPO, LMCL and LCCL were not significantly influenced. Tench: PB increased all monooxygenase reactions (EN, ECOD, BCDB and EROD), though only significantly ECOD; H2O2 was elevated only after treatment with 0.1 mg/l PB, whereas LPO was decreased (!) after treatment by all three concentrations, though significantly only after 1.0 mg/l PB. LMCL was depressed (not significantly), but LCCL increased 5fold. TBARS were significantly enhanced. P450 1A1 subtype expression was concentration dependently elevated by PB in gill and liver of both fish and in the heart and kidney of tenches, P450 2B and 3A isoforms expression was induced in brain, gill, heart, liver and gut of both fish and in the kidney of tenches. In summary, the increased activities of the monooxygenase reactions tested and the elevated expression of all three P450 isoforms investigated in certain tissues indicate an induction of the P450 families 1, 2 and 3 by PB in fish.

Oxidative state and histological changes in muscles of mastication after conditioning training

Stress due to endurance training of striated muscles leads to adaptive changes in the distribution of muscle fiber types (i.e. ratio of type I and type II fibers). Moreover, severe training leads to tissue hypoxia and oxidative stress in muscles. In the current study, we examined the relationship between histological changes and oxidative state in muscles of mastication during the acute adaptation phase to a sustained muscle load. Six domestic pigs received build-ups on the molar teeth in order to induce a sustained load of the muscles of mastication for a duration of four weeks. Afterwards the masseter (M1, M2, M3), medial pterygoid (PM), temporal (TP1, TP2), and geniohyoid muscles (GH) were removed and the fiber type distribution was determined by enzyme histochemistry. Additionally, the tissue content of glutathione and lipid peroxidation (LPO) products were measured. The above treatment led to muscle fiber transformation of type II into type I (M1, M2, TP2, PM) and a decrease of the GSH content (M1, M2 and TP2). The changes in the GSH/GSSG ratio were in accordance with the changes in proportions of muscle fiber types, with the lowest GSH/GSSG ratios in the most stressed muscles of the treated animals. No significant changes in LPO products were found. The decrease of the GSH/GSSG ratio in the most stressed muscles indicates an increased intracellular oxidative stress, which may be caused by tissue hypoxia during the chronic phase of muscle adaptation.

Transplantation of fetal liver tissue suspension into the spleens of adult syngenic rats: effects of different cytotoxins on cytochrome P450 isoforms expression and on glycogen content

Syngenic fetal liver tissue suspensions were transplanted into the spleens of adult male Fisher 344 inbred rats. Four months after surgery, transplant recipients and age matched control rats were treated with different cytotoxins (allyl alcohol [AAL], bromobenzene [BBZ], carbon tetrachloride [CCl4], or thioacetamide [TAA]) or the respective solvents 24 or 48 hours before sacrifice. Effects of the cytotoxins on the expression of three cytochrome P450 (P450) isoforms, 1A1, 2B1 and 3A2, within spleens and livers were assessed by immunohistochemistry. Additionally, effects on glycogen content within the hepatocytes were examined. In the livers AAL caused small lesions and fatty degeneration of hepatocytes only in some periportal areas. BBZ led to a perivenous necrosis of single cells only, whereas CCl4 and TAA caused complete necrosis of the centrilobular parenchyma. Treatment with each of the four cytotoxins led to necrosis and fatty degeneration of single or groups of hepatocytes within the intrasplenic transplants. This effect was most pronounced with CCl4 and TAA. The orthotopic livers of both solvent treated transplant recipients and control rats displayed only in few lobules a slight P450 1A1, but in all lobules a strong P450 2B1 and 3A2 expression, all mainly located in the hepatocytes around the central veins. AAL administration led to an increase in the P450 2B1 expression in the perivenous hepatocytes, whereas the staining for P450 1A1 was not affected and that for P450 3A2 in the periportal areas was even decreased. BBZ administration caused a P450 1A1 expression in the periportal hepatocytes but a decrease in this staining of the perivenous cells. The number of hepatocytes positively stained for P450 2B1 and 3A2 in the perivenous and intermediate zones was diminished in comparison to the livers of solvent treated rats. TAA and, more pronounced, CCl4 administration caused a strong reduction in the expression of all three P450 isoforms. Spleens of control rats displayed almost no P450 isoforms expression, independent of the treatment with the cytotoxins. Similar to adult liver, the hepatocytes in the transplant containing spleens showed nearly no P450 1A1, but a noticeable P450 2B1 and 3A2 expression. No staining was observed within the bile duct cells of the intrasplenic transplants. AAL administration slightly reduced the P450 2B1 and 3A2 expression in the transplants. BBZ and, much more pronounced, CCl4 and TAA treatment diminished the staining for all three P450 isoforms. AAL administration led to a marked decrease in the glycogen content of the hepatocytes of the periportal zones of the liver lobules, whereas after BBZ, CCl4 and TAA treatment a strong perivenous reduction in the glycogen content was seen. Similarly, within the intrasplenic transplants a remarkable decline in the glycogen content of the hepatocytes was caused by the treatment with each of the four cytotoxins. Especially after AAL and BBZ treatment the glycogen depletion within both livers and transplants was much more pronounced than the effects on morphology or P450 isoforms expression. It can be concluded that the effects of cytotoxins like AAL, BBZ, CCl4 or TAA seen in normal orthotopic liver are exerted in a similar way also in intrasplenic liver cell transplants.

Transplantation of fetal liver tissue suspension into the spleens of adult syngenic rats: effects of various mitogens and cytotoxins on cytochrome P450 (P450) isoforms expression and on P450 mediated monooxygenase functions

Syngenic fetal liver tissue suspensions were transplanted into the spleens of adult male Fisher 344 inbred rats. Four months after surgery, transplant recipients and age matched control rats were treated with various mitogens (fluorene [FEN], fluorenone [FON] and 2-acetylaminofluorene [AAF]) or cytotoxins (allyl alcohol [AAL], bromobenzene [BBZ] and carbon tetrachloride [CCl4]) or the respective solvents 24 or 48 hours before sacrifice. The expression of three cytochrome P450 (P450) isoforms, 1A1, 2B1 and 3A2, within spleens and livers was assessed by immunohistochemistry and P450 mediated monooxygenase functions in spleen and liver 9000 g supernatants by the model reactions ethoxyresorufin O-deethylation (EROD), ethoxycoumarin O-deethylation (ECOD), and ethylmorphine N-demethylation (EMND). The orthotopic livers of both solvent treated transplant recipients and control rats displayed only in few lobules a slight P450 1A1, but in all lobules a moderate P450 2B1 and 3A2 expression, all mainly located in the hepatocytes around the central veins. Correspondingly, regular EROD, ECOD and EMND activities were observed. Each of the three mitogens increased the P450 1A1 expression in the hepatocytes of the perivenous zones of the liver lobules. FON administration caused an additional P450 1A1 immunostaining in the periportal areas, and AAF treatment a P450 1A1 expression in bile duct epithelia. Also the staining for P450 2B1 and 3A2 in the hepatocytes of the perivenous and intermediate zones of the liver lobules was intensified after treatment with any of the mitogens. The three model reactions were significantly increased within the livers after FEN and FON administration, whereas after AAF treatment only ECOD was enhanced, EROD remained unaffected and EMND was decreased. The cytotoxin AAL caused small lesions and fatty degeneration of hepatocytes only in some periportal areas. BBZ only produced a perivenous necrosis of single cells, whereas CCl4 caused complete necrosis of the centrilobular parenchyma. Immunohistochemically, AAL administration led to an increase in the P450 2B1 expression in the perivenous hepatocytes, whereas the staining for P450 1A1 was not affected and that for P450 3A2 was even decreased in the periportal areas. Due to AAL treatment EROD and EMND activities were not affected and ECOD activity was increased. BBZ administration caused a P450 1A1 expression in the periportal hepatocytes but a decrease in this staining of the perivenous cells. The number of hepatocytes positively stained for P450 2B1 and 3A2 in the perivenous and intermediate zones was diminished in comparison to the livers of solvent treated rats. After BBZ treatment, EROD and EMND activities were decreased, ECOD activity was not affected. CCl4 administration caused a strong reduction in the expression of all three P450 isoforms and in the activity of all three model reactions. Spleens of control rats displayed almost no P450 isoforms expression and P450 mediated monooxygenase functions, without as well as after treatment with the mitogens or cytotoxins. Similar to adult liver, the hepatocytes in the transplant containing spleens showed nearly no P450 1A1, but a noticeable P450 2B1 and 3A2 expression. No staining was observed within the bile duct cells of the intrasplenic transplants.

Transplantation of fetal liver tissue suspension into the spleens of adult syngenic rats: inducibility of cytochrome P450 dependent monooxygenase functions by beta-naphthoflavone, phenobarbital and dexamethasone

In the present study the effects of beta-naphthoflavone (BNF), phenobarbital (PB) and dexamethasone (DEX) on cytochrome P450 (P450) dependent monooxygenase functions were investigated in intrasplenic liver cell explants in comparison to adult liver. Fetal liver tissue suspensions were transplanted into the spleens of 60-90 days old adult male syngenic Fisher 344 inbred rats. 2, 4 or 6 months after surgery, transplant recipients and age matched controls were orally treated with BNF (1x50 mg/kg body weight (b.wt.)), PB (1x50 mg/kg b.wt.), DEX (for 3 days 4 mg/kg b.wt. per day), or the respective solvents (dimethylsulfoxide or 0.9% NaCl). The animals were sacrificed 24 (BNF, DEX) or 48 (PB) hours after the last treatment. P450 mediated monooxygenase functions were measured in spleen and liver 9000 g supernatants by three model reactions for different P450 subtypes: ethoxyresorufin O-deethylation (EROD; 1A), ethoxycoumarin O-deethylation (ECOD; 1A, 2A, 2B), and ethylmorphine N-demethylation (END; 3A). Spleen weights were significantly higher in transplanted rats, compared to controls, at all three time points after surgery. Induction with PB or DEX, and in some cases also with BNF, lead to a significant increase in liver weights of transplant recipients and control rats independent of the time after transplantation. In contrast, there was no influence on spleen weights due to BNF or PB. At all time points after surgery, with DEX a marked decrease in body weights, weights of adrenal glands and of lymphatic organs like thymus glands and spleens was observed, with the weights of the transplant containing spleens being still higher in comparison to control organs. Spleens of control animals displayed nearly no P450 mediated monooxygenase functions neither without nor with induction. After transplantation, however, significant EROD and ECOD, but hardly any END activities were seen in the host organs at all three time points after surgery. In transplant containing spleens EROD and ECOD were significantly increased after BNF or PB treatment at all three time points after surgery, and ECOD after DEX administration, but at 4 and 6 months after transplantation only. END was only induced after DEX treatment at 6 months after transplantation. With the livers of both transplant recipients and control rats EROD and ECOD were increased after BNF induction and EROD, ECOD, and END after PB treatment at all three time points after transplantation. After DEX administration END was significantly enhanced only at 2 and 4 months after transplantation, ECOD was decreased at 2 and 4 months, and EROD was diminished at all three time points after surgery. Transplantation of fetal liver tissue suspensions into the spleens did not influence monooxygenase functions and their inducibility within the respective livers of the animals. These results demonstrate that transplanted liver cells originating from syngenic fetal liver tissue suspensions display P450 dependent monooxygenase functions which are, simi lar to normal adult liver, inducible by BNF, PB and DEX. Both monooxygenase functions and their inducibility within the transplant containing spleens display quantitative and qualitative developmental changes.

The granulated convoluted tubules of the rat submandibular glands under experimental conditions

Granulated convoluted tubules are the specific ductal segment of the submandibular glands of mice and rats. These tubules are functionally integrated into hormonal circuits, produce regulatory peptides as well as epidermal and nerve growth factor. The experimental studies on adult male Wistar and Fischer 344 rats demonstrate acute cytotoxic lesions of the granulated tubules by means of a single dose of 2-acetylaminofluorene. After only a few administrations of the compound the intralobular duct tree is lined by an atrophic epithelium with loss of specific structures, the EGF immunoreactivity and the susceptibility to further cytolethal effects. The early selective damage of the granulated convoluted tubules indicates that the growth factor production and certain drug-metabolizing/drug-excreting capacities are situated within the same ductal segment. It is considered that other systemically administered compounds might also influence this growth factor-producing ductal segment, though less dramatically than 2-acetylaminofluorene.

Investigation on possible antioxidative properties of the NMDA-receptor antagonists ketamine, memantine, and amantadine in comparison to nicanartine in vitro

Possible antioxidative properties of three N-methyl-D-aspartate (NMDA)-receptor antagonists, the anesthetic ketamine and the antiparkinson drugs memantine and amantadine were investigated in vitro on the microsomal cytochrome P450 (P450) system of rat livers and on rat whole blood chemiluminescence in comparison to nicanartine, a substance with known antiatherosclerotic, hypolipemic and antioxidative capacity. For this purpose, the effects on NADPH- and iron-stimulated lipid peroxidation (LPO), hydrogen peroxide (H2O2) production, and NADPH- and iron-stimulated lucigenin (LC) and luminol (LM) amplified chemiluminescence (CL) were examined using rat liver microsomes. Additionally, the influence on LM amplified whole blood chemiluminescence after zymosan activation of polymorphonuclear leukocytes (WB-CL) was investigated. Furthermore, binding to P450 and effects on P450 mediated monooxygenase function, as measured by the model reactions ethoxyresorufin O-deethylation (EROD), ethoxycoumarin O-deethylation (ECOD), and ethylmorphine N-demethylation (END), were assessed. Nicanartine concentration dependently reduced LPO and H2O2 production already at a concentration of 1 microM, whereas LC and LM amplified CL and WB-CL were not affected. EROD and END were concentration dependently diminished starting at 1 microM, and ECOD already at 0.1 microM. Ketamine decreased LPO, H2O2 production and LM and LC amplified CL, starting at 100 microM. WB-CL was significantly diminished already at 10 microM. EROD and ECOD were inhibited at 10 and 100 microM and END at 100 microM. With memantine a concentration dependent inhibition of LPO and WB-CL was seen at 100 and 1000 microM and a reduction of LC and LM amplified CL only at 1000 microM. H2O2 production was not affected. EROD and ECOD were significantly diminished by a concentration of 100 microM. No effect was observed on END. Amantadine significantly reduced LPO and WB-CL, but only at 1000 microM. H2O2 production and LC and LM amplified CL were not affected. EROD was significantly diminished at 100 microM, whereas no influence was seen on ECOD and END. Nicanartine displayed type II or reverse type I, ketamine, memantine and amantadine type I substrate binding to P450. The highest binding affinity to P450 was seen with nicanartine, followed by ketamine, memantine and then amantadine. These results demonstrate, that all four substances seem to act as radical scavengers and/or as inhibitors of the oxidative function of P450. All four substances seem to interfere with the monooxygenase function of P450. This may result in a possible influence on the biotransformation of endogenous as well as of foreign compounds. The effects of nicanartine were much more pronounced than those of ketamine, memantine, and amantadine.

Ciprofibrate--racemate and enantiomers: effects of a four-week treatment on male inbred Fischer rats. A biochemical and morphological study

Ciprofibrates (racemate and both enantiomers, Raccip, R- and Scip) were administered orally in doses of 1 and 10 mg/kg once daily over 28 days to male inbred Fischer 344 rats, age 90-110 days at the beginning of the experiment. Body mass gain was observed in all groups. The 1 mg groups showed almost no difference to the control group. The 10 mg groups exhibited less body mass gain, most pronounced in the Scip group. Liver masses were increased in a dose dependent manner up to more than 200%, only the 10 mg Scip group was not significantly different from the 1 mg group which exhibited an increase in liver weight to about 175%. Also the kidney weights increased to 130%, whereas thymus and spleen weights were decreased in the high dose groups. Liver microsomal cytochromes P450 (P450) concentrations were not altered in the 1 mg groups and distinctly lowered in the 10 mg groups. Ethoxyresorufin and ethoxycoumarin O-deethylations were lowered in all experimental groups in a dose dependent manner, after administration of the high doses down to 30% of the control levels or less. Pentoxyresorufin O-depentylation, however, was increased in all 1 mg groups. In the high dose groups it was not altered. Ethylmorphine N-demethylation was decreased after administration of the high doses by about 50%, but only Scip decreased this reaction also after administration of the low dose. NADPH/Fe2+-stimulated microsomal luminol and lucigenin amplified chemiluminescence was increased, whereas hydrogen peroxide formation was depressed even by the low doses to 50% of the normal values, to about 25% by the high doses. Microsomal lipid peroxidation, however, was only slightly or not influenced. Glutathion concentrations (in the reduced and the oxidized form) were increased in a dose dependent manner by about 20 to 30%, the concentration of lipid peroxides was not significantly influenced. Thus, the effects of the enantiomers were not different and were similar to those of the racemate. In serum, cholesterol and triglycerides were only moderately lowered. Albumin concentrations were significantly enhanced in all groups, total proteins after 1 mg/kg Raccip only. Serum bilirubins were not altered, and among the indicator enzymes for liver damage only ALAT, alkaline phosphatase and the dehydrogenases were increased, in no case higher than twofold. Histologically distinct effects were seen after administration of both doses, more pronounced after 10 mg/kg, but with no differences between the enantiomers and Raccip: marked hypertrophy of the hepatocytes, reduced staining of the nuclei, strongly acidophilic granulated cytoplama, no basophilia of the cell bodies, loss of glycogen. These changes were most pronounced around the central veins. Hepatocyte apoptoses also were observed. By immunohistochemistry an increased staining was seen for all P450 isoforms tested (1A1, 2B1, 2E1, 3A2 and 4A1), predominantly perivenously and most pronounced after administration of the high doses without differences between Rcip, Scip or Raccip (preliminary results). By electron microscopy a moderate proliferation of peroxisomes after treatment with 1 mg/kg Cips with a ratio between mitochondria and peroxisomes of about 1:1 (controls: 10:1) was observed, and the peroxisomes were a more heterogeneous population. The relative portions of glycogen and both forms of the ER decreased. Treatment with 10 mg/kg Rcip, Scip or Raccip led to a strong increase in the number of peroxisomes, in some hepatocytes the ratio between mitochondria and peroxisomes was 1:3 with an increased heterogeneity among the peroxisomes evidenced by a broad range of electron densities. Most peroxisomes lacked a nucleoid. Thus, the biochemical effects differed only slightly and the morphological effects of the enantiomers were not different and were similar to those of the racemate.

Is there a beneficial effect of the calcium channel blocker diltiazem on cyclosporine A nephrotoxicity in rats?

To investigate whether or not there is a beneficial effect of diltiazem (D) on cyclosporine A (CsA) nephrotoxicity, renal function, CsA blood levels, and effects of CsA on biotransformation in the liver and on lipid peroxidation were characterized in rats. A single administration of D (60 mg/kg b.wt.) reduced urinary volume (UV), GFR and excretion of Na+ and K+, whereas a single dose of CsA (60 mg/kg b.wt.) alone had no respective effects. P-aminohippurate excretion was almost equal in all groups. Lower doses of D (and CsA) were without effects. After repeated CsA treatment a retardation in body weight gain was seen, with little effect of a co-administration with D hereon. In all tests, thymus mass was reduced by CsA, the weight of spleen, liver, adrenal glands, and kidney were not generally affected by any of the treatments. Furthermore, after repeated administration of CsA and/or D, urinary volume, GFR and Na+ excretion were reduced by CsA, too. Electrolyte concentrations in plasma showed no evident changes by any of the treatments for Na+ and Ca2+. After long time treatment, CsA and CsA + D quite similarly led to higher K+ but lower Mg2+ concentrations in plasma. Only with 7 days highest dosage treatment PAH excretion was reduced significantly by CsA and CsA + D treatment. Surprisingly, CsA levels measured in blood and in kidney tissue, showed lower values after co-administration with D compared to CsA treatment alone. This could be caused by higher activities of monooxygenase functions revealed after pretreatment with D alone. Reduced glutathione (GSH) contents in kidney were elevated in CsA and CsA + D treated groups. In general no significant differences were to be observed concerning lipid peroxidation and stimulated H2O2 formation. Altogether evident protective effects of diltiazem on CsA nephrotoxicity in rats could not be proven.

Developmental changes of cytochrome P450 dependent monooxygenase functions after transplantation of fetal liver tissue suspension into spleens of adult syngenic rats

Fetal liver tissue suspensions were transplanted into the spleens of adult male syngenic Fisher 344 inbred rats. Animals were sacrificed at 3 days, 1, 2, 4 weeks, and 2, 4 and 6 months after transplantation and cytochrome P450 (P450) dependent monooxygenase functions in spleen and liver 9000 g supernatants were assessed by measuring three model reactions for different P450 subtypes: ethoxyresorufin O-deethylation (EROD; mainly 1A), ethoxycoumarin O-deethylation (ECOD; predominantly 1A, 2A, 2B) and ethylmorphine N-demethylation (END; mainly 3A). Values of transplant recipients were compared to those of sham operated and age matched control rats. Spleen weights were significantly higher in transplanted rats, compared to controls or sham operated animals, but there was no influence of the transplants within the spleens on liver weights. With fetal livers at the 21st day of gestation, the day of transplantation, a weak EROD and ECOD, but no END activity was seen. Spleens of controls or sham operated animals displayed nearly no P450 mediated monooxygenase functions. In the explant containing spleens a significant and increasing EROD activity was found from 4 weeks after surgery on and an ECOD activity already 2 weeks after transplantation. END was only slightly enhanced at 6 months after surgery. The livers of all three groups of rats displayed normal EROD, ECOD and END activities. Transplantation of fetal liver tissue suspensions into the spleens did not influence the P450 dependent monooxygenase functions within the livers of the animals. From these results it can be concluded that intrasplenically transplanted liver cells originating from syngenic fetal liver tissue suspensions proliferate and differentiate within the host organs. They display P450 dependent monooxygenase functions with some developmental changes during the observed time period of 6 months.

Transplantation of fetal liver tissue suspension into the spleens of adult syngenic rats: effects of beta-naphthoflavone, phenobarbital and dexamethasone on cytochrome P450 isoforms expression and on glycogen storage

In the present study, the effect of beta-naphthoflavone (BNF), phenobarbital (PB) and dexamethasone (DEX) on the expression of three cytochrome P450 (P450) isoforms, 1A1, 2B1 and 3A2, and on glycogen storage was investigated in intrasplenic liver cell explants in comparison to adult liver. Fetal liver tissue suspensions were transplanted into the spleens of adult male syngenic Fisher inbred rats. Four months after surgery, transplant recipients and age matched controls were orally treated with BNF (1 x 50 mg/kg body weight (b.wt.)), PB (1 x 50 mg/kg b.wt.), DEX (for 3 days 4 mg/kg b.wt. per day), or the respective solvents (dimethylsulfoxide or 0.9% NaCl). The animals were sacrificed 24 (BNF, DEX) or 48 (PB) hours after the last treatment. The livers of both solvent treated transplant recipients and control rats displayed only in few liver lobules a slight P450 1A1, but in all lobules a strong P450 2B1 and 3A2 expression, which was all mainly located in the hepatocytes around the central veins (zone III, according to Rappaport). After BNF administration a P450 1A1 expression was induced in the hepatocytes of the peripheral regions of the liver lobules (zone I, according to Rappaport), whereas the staining of the hepatocytes around the central veins disappeared. Also the staining for P450 2B1 in the hepatocytes of zone III became slightly more pronounced. Following PB treatment the P450 1A1 expression in the hepatocytes of the central regions (zone III), as seen in few lobules after solvent treatment only, was reduced, whereas the staining for P450 2B1 and 3A2 was more pronounced in the hepatocytes of the intermedial and central regions of the liver lobules (zone II and III). DEX treatment diminished P450 1A1 and 2B1 expression within the livers of both transplant recipients and control rats. In contrast, the staining for P450 3A2 was enhanced in all regions of the liver lobules. Transplantation of fetal liver tissue suspensions into the spleens did not influence the inducibility of P450 isoforms expression within the respective livers of the animals. Spleens of control rats displayed no P450 isoforms expression without as well as with induction. In the explant containing spleens, however, similar to normal liver, the transplanted hepatocytes displayed nearly no P450 1A1, but a strong P450 2B1 and 3A2 expression. After BNF treatment a staining for P450 1A1 was induced and also the P450 2B1 expression was slightly more pronounced. PB treatment caused an increase in the staining for P450 2B1 and 3A2 and DEX administration for P450 3A2 within the transplanted hepatocytes. Additionally, after DEX treatment some bile ducts of the explants displayed a slight staining for P450 1A1, 2B1 and 3A2. All hepatocytes within the livers of both solvent treated transplant recipients and control rats displayed a slightly PAS-positive cytoplasma and, in most cases, homogeneously distributed, fine-grained, strongly PAS-stained granules indicating glycogen storage. No regional variance in the glycogen content of the hepatocytes was seen within the liver lobules, but there was a marked difference between the individual hepatocytes of the same lobular region in the extent of glycogen accumulation. The hepatocytes within the explants displayed the same type of glycogen storage as did the adult liver cells. BNF treatment did not display any effect on the glycogen accumulation in livers and intrasplenic liver cell explants. After PB administration, only in livers, but not in the transplants, the glycogen content in the hepatocytes around the central veins was slightly reduced. DEX treatment lead to an excessive storage of fat within the hepatocytes of both livers and spleens. Thus, the glycogen was displaced, leading to a "spoke-wheel" like pattern of glycogen storage. Additionally, within the hepatocytes of both livers and liver cell explants a higher amount of glycogen seemed to be stored and the granules appeared to be more coarse-grained. (ABSTRACT

Influence of different transplantation methods on liver cell survival in spleens of rats

Isolated hepatocytes, liver tissue suspensions, or liver tissue cylinders from biopsies were transplanted into the spleens of adult male rats. Donors were syngenic fetuses, syngenic or allogenic adult rats, or autologous material was obtained from the rat's own liver. The outcome of the different transplantation procedures was evaluated at 1 and 6 months after surgery. Additionally the influence of a 30% hepatectomy (HX) on the result of the transplantation was investigated. When fetal material was transplanted, the best results in sequence with respect to the number of viable hepatocytes within the spleens were obtained (1) after transplantation of syngenic fetal liver tissue suspensions, (2) syngenic fetal liver tissue cylinders and (3) syngenic fetal isolated hepatocytes. HX only improved the results with transplantation of syngenic fetal isolated hepatocytes. After transplantation of syngenic fetal liver tissue suspensions and isolated hepatocytes, but not after transplantation of syngenic fetal liver tissue cylinders, the number of hepatocytes was higher at 6 months than at 1 month after surgery. Concerning syngenic adult liver material, only transplantation of isolated hepatocytes lead to a remarkable and increasing number of surviving hepatocytes at both 1 and 6 months after surgery. These results were further improved by HX. With syngenic adult liver, the other transplantation methods yielded no or nearly no viable hepatocytes in the spleens. In comparison to the results after transplantation of syngenic fetal liver tissue suspensions, transplantation of syngenic adult isolated hepatocytes was less efficient, but still yielded more viable hepatocytes than the transplantation of syngenic fetal isolated hepatocytes. After transplantation of autologous liver tissue suspensions, autologous liver tissue cylinders or allogenic adult liver material only few surviving hepatocytes were observed. At 1 month after transplantation of syngenic fetal liver material, syngenic adult isolated hepatocytes or autologous liver tissue cylinders into the spleens 40-80% of the explants consisted of bile ducts independent from the transplantation method. At 6 months after surgery the bile ducts were much less and in some cases no longer visible. After transplantation of autologous liver tissue suspensions or allogenic adult liver material only very few bile ducts were seen, but anyhow in those cases only poor results were obtained. Thus, with respect to transplantation outcome and long-term liver cell survival, intrasplenic transplantation of both syngenic fetal liver tissue suspensions and syngenic adult isolated hepatocytes seem to be the most suitable methods and should be chosen for further investigations on explant morphology and function.

Developmental expression of cytochrome P450 isoforms after transplantation of fetal liver tissue suspension into the spleens of adult syngenic rats

In the present study, the developmental expression of three cytochrome P450 (P450) isoforms, 1A1, 2B1 and 3A2, and the ability to store glycogen was investigated in intrasplenic liver cell explants in comparison to adult and fetal liver. Fetal liver tissue suspensions were transplanted into the spleens of adult male syngenic Fisher inbred rats. Animals were sacrificed at 3 days, 1, 2, 4 weeks, 2, 4, 6 months and 1 year after transplantation. Spleens and livers of transplant recipients were compared to those of sham operated and control rats. Three days after transplantation little bulks of hepatocytes and only few bile ducts were seen in the red pulp of the transplant containing spleens. A massive hypertrophy and proliferation of bile ducts and also an augmentation in the number of hepatocytes were observed 4 weeks after transplantation. One month later, however, the bile ducts had become more and more atrophic, while instead the number of hepatocytes continuously increased. One year after surgery large masses of hepatocytes with apparent cord structure and only few but well preserved bile ducts were seen. Within the livers of adult rats, P450 1A1 was only slightly expressed by some hepatocytes around the central veins. P450 2B1 and 3A2 isoforms expression was much stronger, but also predominantly located in the hepatocytes of the central zone of the liver lobule. Hepatocytes of fetal livers displayed a moderate P450 1A1 expression. In some cells also a very mild staining for P450 2B1 and 3A2 was observed. Within the hepatocytes of the intrasplenic liver cell explants P450 1A1 was still expressed 3 days after transplantation, disappeared at 1 week after surgery, but reappeared at 4 weeks after transplantation. After 2, 4 and 6 months no staining for P450 1A1 was detectable any more. One year after transplantation again a slight P450 1A1 expression appeared. With P450 2B1 and 3A2 a mild to moderate expression was seen already at 3 days after transplantation. Four weeks after surgery nearly all of the hepatocytes were stained for P450 2B1 and 3A2, but there were marked differences between the individual cells in the extent of the expression of these two P450 subtypes, like it was also the case with normal adult liver. Within hepatocytes of the fetal livers strongly stained glycogen granules were seen, which, in comparison to adult livers, were rather coarse-grained. Three days after transplantation the glycogen granules in the transplanted hepatocytes were still coarse-grained, but from 1 week after transplantation on, they became more and more fine-grained. As it was also the case with normal adult liver cells, there were marked differences between the individual transplanted hepatocytes in their glycogen content. These results demonstrate that transplanted liver cells originating from syngenic fetal liver tissue suspensions can survive in host organs like the spleen for at least 1 year. They proliferate, differentiate, are able to store glycogen, and express different P450 isoforms, like normal adult liver cells.

The effects of incentive on antisaccades: is a dopaminergic mechanism involved?

The effect of incentive was investigated upon performance in the antisaccade (AS), memory saccade (MS) and reflexive saccade (RS) task, alone and following performance in tasks of a psychometric battery. Accuracy performance (correct saccades) in the AS and MS task is dependent on two prefrontal functions, the preservation of transient information across short time intervals and the inhibition of prepotent but inappropriate responses, and is impaired in patient populations with known prefrontal dysfunction. It was predicted that, in normal humans, incentive will improve accuracy performance in the AS and MS task, leaving performance in the RS task unaffected (study 1). Saccades were recorded in 24 healthy young male volunteers. Measurements of saccades were performed (in the presence and absence of monetary incentive) alone or following performance on a psychometric test battery that included tasks of working memory, vigilance, attention and psychomotor activity. Incentive increased the number of correct saccades in the AS task and the performance index in the working memory task. No other direct changes were seen in the presence of incentive. The role of dopamine in performance in the AS compared to the RS task was investigated subsequently in study 2. Twenty healthy young male volunteers received levodopa and benserazide (100 and 25 mg, respectively) orally, and 1 and 5 h later measurements of AS and RS were performed. Levodopa significantly decreased the number of correct saccades in the AS task. No other effects were seen. These data, taken together, suggest, first, that the accuracy performance in the AS task is more sensitive than in the MS or RS task, to positive incentive due to monetary reward; and second, that the dopaminergic system may mediate such an effect, because levodopa, a dopaminergic drug, influenced the same performance measurement. The relationship, however, between these two manipulations (incentive and administration of dopaminergic drugs) is not clear, because incentive improved and levodopa impaired performance.

Endogenous noradrenaline activates alpha 2-adrenoceptors on serotonergic nerve endings in human and rat neocortex

Slices from human neocortex preincubated with [3H]serotonin ([3H]5-HT) were superfused and stimulated electrically to investigate whether the alpha 2-adrenoceptors on serotonergic terminals can be stimulated by endogenous noradrenaline (NA) released from neighboring noradrenergic fibers. The stimulation-evoked 3H overflow, representing action potential-induced, exocytotic release of 5-HT, was depressed by the NA uptake blocker (+)-oxaprotiline. Rauwolscine (a mixed alpha 2-adrenoceptor antagonist/5-HT autoreceptor agonist) or phentolamine [a combined alpha-adrenoceptor/5-HT autoreceptor antagonist; the latter drug in the presence of (+)-oxaprotiline] enhanced the release when the 5-HT autoreceptors had previously been blocked by metitepine. Under hypothermia the release of 5-HT was found to be decreased and that of NA to be increased; under these conditions idazoxan (an alpha 2-adrenoceptor antagonist) enhanced the release of 5-HT. In neocortex slices from rats (+)-oxaprotiline similarly depressed the release of 5-HT (measured with the same methods) as in human tissue. When rats were pretreated with 6-hydroxydopamine, the inhibitory effect of exogenous NA on 5-HT release was increased, and in slices from rats pretreated with desipramine, it was decreased. In conclusion, alpha 2-heteroreceptors can be activated by endogenous NA released from neighboring noradrenergic fibers. Because regulatory processes analogous to those in rats probably occur in humans as well, an up- or down-regulation of alpha 2-heteroreceptors in depressed patients with a (pathological) decrease or a (therapeutic) enhancement of the noradrenergic neurotransmission may also be assumed to occur.

Different effects of 1-methyl-4-phenyl-pyridinium (MPP+) on monoamine oxidase of dopaminergic terminals in caudate nucleus slices from pigmented and from albino rabbits

Slices of caudate nucleus from pigmented and from albino rabbits were preincubated in vitro for 24 h with different concentrations of the neurotoxic compound MPP+. Subsequently, endogenous dopamine (DA) in the slices was determined by HPLC. MPP+ (1 and 3.2 mumol/l) was more effective in diminishing DA levels in caudate nucleus slices from albino than in slices from pigmented rabbits. Following 24 h pretreatment with MPP+, the accumulation of [3H]-DA in caudate nucleus slices from pigmented rabbits was either enhanced (at 0.32 mumol/l, 1 mumol/l and 3.2 mumol/l MPP+) or reduced (at 32 mumol/l MPP+). In contrast, MPP+ did not enhance the accumulation of [3H]-DA in caudate nucleus tissue from albino rabbits and was more potent in reducing the [3H]-DA content in slices from albino than in slices from pigmented rabbits. When the selective type A monoamine oxidase (MAO) inhibitor clorgyline was present during pre-incubation, but not when the selective type B MAO inhibitor deprenyl was, the concentration-response curve for MPP+ with caudate nucleus slices from pigmented rabbits was similar to that obtained with slices from albino rabbits. Clorgyline and deprenyl did not change the effects of MPP+ in caudate nucleus slices from albino rabbits. These findings are compatible with the hypothesis that the MAO within dopaminergic terminals in the caudate nucleus of pigmented, but not of albino, rabbits is of type A since MAO-A is preferentially inhibited by MPP+. In line with this hypothesis, the accumulation of the preferential MAO-A substrate [3H]-5-HT in caudate nucleus slices from pigmented rabbits was about 39% lower than that in slices from albino rabbits.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitory effects of the antiparkinsonian drugs memantine and amantadine on N-methyl-D-aspartate-evoked acetylcholine release in the rabbit caudate nucleus in vitro

Slices of the rabbit caudate nucleus were incubated with [3H]choline or [3H]dopamine and then superfused continuously with Mg(++)-free medium. Stimulation with N-methyl-D-aspartate (NMDA), alpha-amino-2,3-dihydro-5-methyl-3-oxo-4-isoxazolepropanoic acid (AMPA), L-glutamate and kainic acid (in that rank order of potencies) caused a concentration-dependent increase in [3H]ACh efflux, which was abolished in the presence of Mg++. This kind of release was Ca(++)-dependent and tetrodotoxin-sensitive. In contrast, NMDA was hardly effective in stimulating [3H]ACh release from hippocampal or cortical slices, as well as [3H]dopamine release from slices of rabbit caudate nucleus. Hence, the presence of cell bodies of stimulated neurons seems to be a prerequisite for the induction of release via NMDA receptors. Dizocilpine [(+)-5-methyl-10,11-dihydro-5H-dibenzo(a,d)cyclohepten-5,10-imine maleate] at nanomolar concentrations, as well as memantine and amantadine at low micromolar concentrations, inhibited the L-glutamate- and NMDA-evoked [3H]ACh release in a concentration-dependent, noncompetitive and use-dependent manner. Also (+/-)-2-amino-5-phosphopentanoic acid at micromolar concentrations depressed the L-glutamate- and NMDA-induced release, acting, however, in a competitive manner. It is concluded that, by antagonizing NMDA receptor-mediated ACh release, memantine and amantadine may act as functional "anticholinergics" when administered clinically to treat Parkinson's disease.

Quantitative evaluation of the autoinhibitory feedback of release of 5-HT in the caudate nucleus of the rabbit where an endogenous tone on α2-adrenoceptors does not exist

Slices of caudate nucleus of the rabbit were preincubated with [3H]serotonin [( 3H]5-HT) in the presence of nomifensine, then superfused and twice stimulated electrically. The stimulation-evoked overflow of tritium, representing action potential-induced, exocytotic release of 5-HT, was inhibited concentration-dependently by 5-HT receptor ligands, the potencies of which were compatible with the assumption of a 5-HT1D-like autoreceptor. The inhibitor of the uptake of 5-HT, 6-nitroquipazine, markedly changed the shape of the concentration-response curve of the 5-HT autoreceptor agonist, 5-carboxamido-tryptamine (5-COHT). The maximum effects of the concentration-response curves of 5-COHT and of exogenous 5-HT became more pronounced in the additional presence of the 5-HT autoreceptor antagonists, metitepin or metergoline. Nonlinear regression analysis of these curves was used to estimate the pKd-value of endogenous 5-HT and the 5-HT biophase concentration at the autoreceptor, in the absence and in the presence of 6-nitroquipazine and in the additional presence of metitepin or metergoline. This revealed a highly operative autoinhibitory feedback, via a 5-HT1D type autoreceptor of release of 5-HT in tissue from the caudate nucleus. Also the inhibition by the alpha 2-adrenoceptor agonists, clonidine and UK-14,304, of release of 5-HT was concentration-dependent. There was neither an enhancement of release by rauwolscine, being a 5-HT autoreceptor agonist and alpha 2-adrenoceptor antagonist, in the presence of metitepin, or by the alpha-adrenoceptor antagonist, phentolamine (10(-6) M).(ABSTRACT TRUNCATED AT 250 WORDS)

Different effects of serotonin (5-HT) uptake blockers in caudate nucleus and hippocampus of the rabbit: role of monoamine oxidase in dopaminergic terminals

Slices of rabbit hippocampus or caudate nucleus were incubated with [3H]-5-HT (0.1 microM, 60 min) or with [3H]-DA. In hippocampal tissue, the 5-HT uptake blockers chlorimipramine, fluvoxamine, and 6-nitroquipazine (0.1, 1, 10 microM) reduced the percentage content of [3H]-5-HT in a concentration dependent manner. The degree of inhibition of [3H]-5-HT content produced by the 5-HT uptake inhibitors was not affected by the MAO inhibitors pargyline or amezinium (which by themselves enhanced [3H] loading) or the catecholamine uptake inhibitor nomifensine (which by itself did not affect [3H] loading). In caudate nucleus tissue, however, the [3H]-5-HT accumulation was reduced only at the highest concentration of the 5-HT uptake blockers (10 microM). In the additional presence of the MAO inhibitors or nomifensine (which by themselves increased or diminished, respectively, the [3H] labelling) the 5-HT uptake inhibitors became more potent in reducing the percentage [3H]-5-HT accumulation of caudate nucleus slices. These results indicate (1) that a false labelling of [3H]-5-HT into dopaminergic terminals in the caudate nucleus can be prevented by nomifensine, (2) that the 5-HT uptake blockers seem to accumulate within the dopaminergic terminals, where they may display a MAO inhibitory property. The 5-HT uptake blockers were ineffective on the percentage tritium accumulation of caudate nucleus slices incubated with [3H]-DA, regardless of the presence of pargyline or nomifensine. Tritiated DA and deaminated [3H]-metabolites were separated in the superfusate of [3H]-DA-release experiments in caudate nucleus tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

The conditions of Ca2+ entry via L-type channels for induction of serotonin release from rabbit hippocampus

The L-type voltage-sensitive calcium channel (VSCC) agonists of the dihydropyridine (DHP) type, Bay K 8644 and (+)-202-791, concentration dependently enhanced the K+ (26.2 mM)-induced 5-HT release from slices of rabbit hippocampus prelabelled with [3H]5-HT when the slices were treated with the monoamine oxidase (MAO) inhibitor, pargyline. The DHP agonists were ineffective on K+ (26.2 mM)-induced release in the absence of pargyline. However, when omega-conotoxin GVIA pretreatment of the slices irreversibly blocked N-type VSCCs, (+)-202-791 markedly enhanced the release of 5-HT evoked by 26.2 mM K+. Thus, at this rather strong stimulus intensity either an increase in the (preferentially cytoplasmic) transmitter pool or blockade of N-type VSCCs was necessary in order to unmask agonist-activated L-type VSCCs. Reduction of the depolarization intensity from 26.2 to 17.2 mM K+, given for 8 min, strongly intensified the stimulatory effects of L-type VSCC agonists irrespective of the use of pargyline under these conditions. The concentration-response curve of (+)-202-791 was 'competitively' shifted to the right by the enantiomer, (-)-202-791, with a pA2 value of 8.6. In conclusion, N- and L-type VSCCs seem to differ in their relation to the cellular machinery for 5-HT release, the latter getting markedly operative when a weak and sustained depolarization is applied or when N-type VSCCs are blocked or when the cytoplasmic transmitter pool is expanded by inhibition of MAO.

Distribution of [125I]omega-conotoxin GVIA and [3H]isradipine binding sites in the central nervous system of rats of different ages

Potential age-related changes in L- and N-type voltage-sensitive calcium channels (L- and N-VSCCs) were assessed by the in vitro binding of [3H]isradipine ([3H]ISR, 150 pM) and [125]omega-conotoxin GVIA ([125I]omega-CT, 4 pM) to membranes prepared from discrete central nervous system regions of 0.5-, 2-, and 18-month-old rats. The rank orders of [3H]ISR and [125I]omega-CT binding, although differing, indicated that the highest binding was in neocortex, corpus striatum, and hippocampus; radioligand binding was generally not affected by the variable of age. These results suggest that the nonidentical [3H]ISR and [125I]omega-CT binding sites are concentrated in those regions characterized by high densities of synaptic connections, and that these sites, as presumed components of L- and N-VSCCs, are relatively stable during the aging process.

Intrastriatal dopaminergic grafts restore inhibitory control over striatal cholinergic neurons

The aim of the study was to examine the influence of intrastriatal dopaminergic grafts on the functioning of striatal cholinergic neurons using an in vitro superfusion method. Rats bearing unilateral 6-hydroxydopamine lesion of the nigrostriatal dopaminergic system received a cell suspension obtained from ED 14 rat embryonic mesencephali which was injected into the denervated striatum. Lesioned animals displayed an ipsilateral rotation in response to amphetamine (5 mg/kg i.p.). This rotational response disappeared following grafting and there was even a significant contralateral rotation in response to the drug. Apomorphine (0.1 mg/kg s.c.) induced a contralateral rotation following the lesion. This latter response was attenuated in the grafted group. Three months after grafting 350 microns thick slices were prepared from striata from the control and experimental sides of lesioned and graft-bearing animals. The slices were preincubated either with 3H-dopamine (10(-7) M) or 3H-choline (10(-7) M) and then superfused with an oxygenated Krebs-Ringer solution. Stimulation with electrical pulses following preincubation with 3H-dopamine elicited a marked increase of tritium outflow from control slices. Stimulation-evoked overflow was of similar magnitude from slices from striata containing the graft, while it was much reduced in slices from lesioned striata. Amphetamine markedly potentiated the effect of electrical stimulation in slices obtained from control and graft-containing striata. Nomifensine (a dopamine uptake blocker) led to a significant decrease of the overflow of 3H-acetylcholine evoked by electrical stimulation from control striatal slices. This inhibition was antagonized by domperidone, a D2 dopamine receptor blocker, a finding which indicates that the action of nomifensine was indeed due to a potentiation of the action of endogenous dopamine released by the electrical stimulation. A similar, although somewhat attenuated, action of nomifensine and domperidone was observed for striatal slices containing the graft. Amphetamine inhibited the stimulation evoked overflow of 3H-acetylcholine in a dose-dependent manner from striatal slices obtained both from the intact and experimental sides of graft-bearing animals, while it had no action on slices from denervated striata. Finally, the dose-response curve for the inhibition of 3H-acetylcholine release by apomorphine was significantly shifted to the left for slices from the lesioned striata as compared with control slices. This leftward shift was totally abolished in the slices from the graft-containing striatum.(ABSTRACT TRUNCATED AT 400 WORDS)

Omega-conotoxin GVIA and pharmacological modulation of hippocampal noradrenaline release

The tritium overflow evoked by electrical stimulation of rabbit hippocampal slices labeled with [3H]noradrenaline was inhibited by omega-conotoxin GVIA, a peptide modulator of the N-type voltage-sensitive calcium channel (N-VSCC). The magnitude of this inhibition was unchanged in the presence of substances which interact with N- and/or L-VSCCs (cadmium, neomycin, (-)- and (+)-202-791), alpha 2-adrenoceptors (idazoxan, UK-14304), protein kinase C (4 beta-phorbol-12,13-dibutyrate) or potassium channels (4-aminopyridine). This finding suggests that the attenuation of calcium-dependent neurotransmitter release by omega-conotoxin GVIA is relatively insensitive to alterations of such release effected by other substances.

Inhibition of central neurotransmitter release by omega-conotoxin GVIA, a peptide modulator of the N-type voltage-sensitive calcium channel

Tritium overflows, evoked by electrical stimulation (2 min; 2 ms, 3 Hz, 5 V/cm, and 24 mA) of [3H]-dopamine-, [3H]-noradrenaline-, [3H]-5-hydroxytryptamine, and [3H]-acetylcholine-labeled slices prepared from discrete regions of the rabbit central nervous system, were inhibited 39-50% by omega-conotoxin GVIA (omega-CT; 5 nmol/l), a peptide modulator of the N-type voltage-sensitive calcium channel (N-VSCC). Additional experiments using omega-CT (5 nmol/l) and [3H]-noradrenaline-labeled hippocampal slices indicated the time dependence of omega-CT-induced inhibition, the competitive antagonism between buffer calcium concentration and omega-CT, and the lack of effect of prolonged electrical stimulation (15 min; 0.4 Hz) on omega-CT-induced inhibition. These various results suggest that 1) omega-CT competes with calcium for the N-VSCC, 2) the inhibitory effects of omega-CT are independent of the gating state of the N-VSCC, and 3) the molecular nature of the N-VSCC may be similar or identical across central neurotransmitter systems. omega-CT appears to be a useful pharmacological tool in studying the involvement of the N-VSCC in neurotransmitter release.

The serotonin (5-HT) autoreceptor in the hippocampus of the rabbit: role of 5-HT biophase concentration

Slices of hippocampus from the rabbit were preincubated with [3H]5-HT), then superfused continuously and twice stimulated electrically. The stimulation-evoked overflow of tritium was inhibited by the 5-HT autoreceptor ligands 5-carboxamido-tryptamine (5-COHT), 5-HT, 5-methoxy-N,N-dimethyl-tryptamine (5-MeOMT), (+/-)-8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), methysergide and (+/-)-cyanopindolol in a concentration-dependent manner. These effects were competitively inhibited by the 5-HT autoreceptor antagonists, metitepin and metergoline. (+/-)-Cyanopindolol also reduced the evoked release of 5-HT from slices of cortex from the rat. The inhibitor of the uptake of 5-HT, 6-nitroquipazine diminished the autoreceptor-mediated depression of release of 5-HT. In cortex tissue from the rat, 6-nitroquipazine reversed the decreased release of 5-HT, due to (+/-)-cyanopindolol, to a facilitation. The disinhibition of the release of 5-HT by autoreceptor antagonists was further enhanced by 6-nitroquipazine. Non-linear regression analysis of concentration-response curves for 5-COHT yielded the following pKd of endogenous 5-HT at the autoreceptor: 7.753 +/- 0.116. This value corresponds to the pKd of 5-HT at the 5-HT1B binding site. The 5-HT biophase concentration at the autoreceptor of 10(-8.220 +/- 0.132)M was markedly enhanced by 6-nitroquipazine (10(-6)M) to 10(-7.476 +/- 0.132)M. It is concluded that the 5-HT autoreceptor belongs to the 5-HT1B subtype of receptor; the corresponding 5-HT biophase concentration can be estimated quantitatively; 8-OH-DPAT decreased the evoked release of 5-HT through both 5-HT autoreceptors and alpha 2-heteroreceptors and (+/-)-cyanopindolol acts as partial agonist at the 5-HT autoreceptor.

False labelling of dopaminergic terminals in the rabbit caudate nucleus: uptake and release of [3H]-5-hydroxytryptamine

The effect of the catecholamine uptake inhibitor nomifensine and of the 5-hydroxytryptamine (5-HT) uptake blocker 6-nitroquipazine on the accumulation of [3H]-5-HT (0.1 microM, 60 min incubation) and [3H]-dopamine (0.1 microM, 30 min incubation) into slices of hippocampus and caudate nucleus of the rabbit was investigated. In addition, the influence of nomifensine on the electrically evoked [3H]-5-HT release from caudate nucleus slices and of nomifensine and 6-nitroquipazine on [3H]-5-HT released from caudate nucleus slices was analysed. In hippocampal slices, which contain practically no dopaminergic but densely distributed 5-hydroxytryptaminergic and noradrenergic nerve terminals (ratio of dopamine:5-HT:noradrenaline about 1:30:25), nomifensine (1, 10 microM) did not affect the accumulation of [3H]-5-HT; 6-nitroquipazine (1 microM) reduced [3H]-5-HT uptake to about 35% of controls. In the caudate nucleus, however, where dopamine is the predominant monoamine (ratio of dopamine:5-HT:noradrenaline about 400:25:15) nomifensine (1, 10 microM) reduced the tritium accumulation to 65% whereas 6-nitroquipazine (1 microM) was ineffective. The combination of both drugs (1 microM each) led to a further decrease to about 15%. The uptake of [3H]-dopamine into hippocampal slices was blocked by both nomifensine (1 microM) and 6-nitroquipazine (1 microM) whereas in caudate nucleus slices only nomifensine (1, 10 microM) reduced the accumulation of [3H]-dopamine. The combination of both drugs was not more effective than nomifensine alone. The different effects of both uptake inhibitors in the hippocampus and caudate nucleus suggest a neurone specific rather than a substrate specific mode of action. 4 In caudate nucleus slices incubated with [3H]-5-HT and superfused continuously the electrically evoked 5-HT release was diminished by the D2-dopamine receptor agonist LY 171555 and enhanced by the D2-receptor antagonist domperidone. If, however, the labelling of caudate nucleus slices was performed in the presence of I microM or 1O microM nomifensine, the modulation of 5-HT release via D2- receptors was reduced or abolished, respectively. In the hippocampus both LY 171555 and domperidone were completely ineffective in modulating 5-HT release regardless of the absence or presence of nomifensine. 5 The present results indicate that an inverse cross labelling of [3H]-5-HT into dopaminergic and of [3H]-dopamine into 5-hydroxytryptaminergic terminals may occur despite the low concentration (0.1 microM) oftritiated transmitters used. Such cross labelling, as demonstrated with the incubation period of 60 min in the caudate nucleus, may falsely indicate the existence of D2-dopamine receptors modulating [3H]-5-HT release. If both 5-hydroxytryptaminergic and dopaminergic terminals are present within the brain region under investigation false labelling can be corrected using neuronally specific uptake inhibitors.