Characterization and therapeutic application of canine adipose mesenchymal stem cells to treat elbow osteoarthritis

Visceral adipose tissue (AT) obtained from surgical waste during routine ovariectomies was used as a source for isolating canine mesenchymal stem cells (MSCs). As determined by cytofluorimetry, passage 2 cells expressed MSC markers CD44 and CD90 and were negative for lineage-specific markers CD34 and CD45. The cells differentiated toward osteogenic, adipogenic, and chondrogenic directions. With therapeutic aims, 30 dogs (39 joints) suffering from elbow dysplasia (ED) and osteoarthritis (OA) were intra-articularly transplanted with allogeneic MSCs suspended in 0.5% hyaluronic acid (HA). A highly significant improvement was achieved without any medication as demonstrated by the degree of lameness during the follow-up period of 1 y. Control arthroscopy of 1 transplanted dog indicated that the cartilage had regenerated. Histological analysis of the cartilage biopsy confirmed that the regenerated cartilage was of hyaline type. These results demonstrate that transplantation of allogeneic adipose tissue-derived mesenchymal stem cells (AT-MSCs) is a novel, noninvasive, and highly effective therapeutic tool in treating canine elbow dysplasia.

In vivo comparative study of the seizure- and ischemia-induced synthesis of eicosanoids in the brain of gerbils

After transient cerebral ischemia induced by bilateral ligation of carotid arteries, followed by 5 min reperfusion, concentrations of prostaglandin D2 and LTC4-like material increased with time in the gerbil brain. At least a 1 min occlusion time was necessary to elevate the eicosanoid concentrations significantly over the basal levels. Spontaneous tonic-clonic seizures of about 20 sec duration induced an increase in prostaglandin D2 and LTC4-like material comparable to the values found after a 2 min occlusion time. Following carotid artery occlusion, the eicosanoid levels were found to be elevated in midbrain, hypothalamus, striatum, hippocampus and cortex, i.e., those brain areas dependent upon the blood supply from the carotid arteries. In contrast, following spontaneous seizures, prostaglandin D2 concentrations were increased in the striatum, hippocampus and cortex only, and the LTC4-like material in the cortex. Hippocampus, striatum and cortex are brain areas which participate in the generation and propagation of seizures. It appears, therefore, unlikely that the seizure-induced eicosanoid synthesis is triggered off by a hypoxic event due to an impaired breathing caused by convulsions. The regional pattern of the eicosanoid synthesis following the seizures may rather depend on the intensity of the neuronal activity than on regional differences in the eicosanoid-synthesizing capacity.

The phorbol ester TPA potentiates cholera toxin- and isoproterenol-stimulated cyclic AMP-synthesis in primary astrocyte cultures

Cellular responses to changes in the extracellular environment are mediated by intracellular signaling systems. One of the most extensively studied systems is adenylate cyclase which generates the second messenger molecule cAMP. Another one is the phosphatidylinositol (PI) second messenger system giving rise to IP3 and diacylglycerol, the latter stimulating protein kinase C. Recently, a third potential signaling system has attracted increased scientific attention: the phospholipase A2 system which generates arachidonic acid. This substance may be used for eicosanoid synthesis or serve as a second messenger molecule. The present report gives more evidence about mechanisms how these signaling pathways interact in cultured astrocytes. Substances commonly used for stimulation of arachidonic acid release and prostaglandin synthesis in these cultures (A23187, TPA) had no influence on intracellular cAMP levels. Pertussis toxin that had previously been shown to inhibit prostaglandin synthesis, had no influence on cAMP levels either. Cholera toxin, however, raised intracellular cAMP significantly, although much less than the beta-adrenoceptor agonist isoproterenol. Cholera toxin also caused a marked change in astroglial morphology even at reduced concentrations (1-10 ng/ml). A23187 used in combination with Ctx had a moderate stimulatory effect on cAMP synthesis. In contrast, in the presence of Ctx, the PKC-activating phorbol ester TPA synergistically stimulated cAMP production, raising cAMP levels as high as isoproterenol-stimulated levels. The TPA effect was concentration-dependent. It was also dependent on an intact PKC since preincubation of cells with the phorbol ester completely abolished the synergistic effect. The synergistic effect of the phorbol ester was also observed at subthreshold concentrations of isoproterenol. The data reveal that the sole activation of most Gs molecules is a necessary but not sufficient prerequisite to achieve maximal adenylate cyclase activity. The fine-tuning of this activity apparently occurs at the catalytic subunit which is under the (partial) control of phosphorylation by PKC.

Meningocortical lesion increases expression of the cholecystokinin gene in rat cerebral cortex: evidence for the involvement of platelet-activating factor (PAF)

In rat neocortex, interneurons express the gene encoding cholecystokinin. After an injury to the meninges and the underlying cortex the levels of cholecystokinin mRNA are transiently enhanced in the ipsilateral hemisphere. In the present study, we have investigated, whether platelet-activating factor plays a role in this phenomenon. Two antagonists of platelet-activating receptors, i.e. WEB 2086 (1.5 mg/kg) and brotizolam (10 mg/kg), were used. When injected 30 min prior to the injury of the parietal cortex, both agents reduced the rise in the concentration of cholecystokinin mRNA in frontal cortex by approximately 60%. They had no significant effect when given 30 min after the injury. Our finding that antagonists of platelet-activating factor receptors diminish the injury-induced change in the activity of cholecystokinin-interneurons opens the possibility that these agents may also affect other pathophysiological aspects of brain trauma.

Differential prostaglandin formation induced by convulsions in the brain of mice susceptible (DBA/2J) and resistant (CFLP) to acoustic stimulation

Endogenous cerebral prostanoids possess anticonvulsant properties. This study investigates possible age-dependent anomalies of prostanoid synthesis in the brain of seizure-prone DBA/2J (DBA2) mice as compared to sound stimulus-resistant CFLP mice. Irrespective of the age of the animals, a large increase of prostaglandin (PG) D2 and E2 in the brain of CFLP mice was observed in response to pentylenetetrazol (PTZ)-, or electroshock (ES)-induced seizures. Significantly less PGD2 and PGE2 was formed in the brain of DBA2 mice at day 21 after birth when subjected to PTZ or ES convulsions. At 42 days of age, however, this deficit of cerebral PGD2 synthesis in DBA2 mice disappeared concomitantly with the age-related decrease in audiogenic seizure (AS) susceptibility, whereas the deficit of PGE2 formation persisted. These results suggest that a deficiency of cerebral PGD2 synthesis may be one of the factors responsible for the AS susceptibility of the DBA2 mice. In contrast to PTZ or ES convulsions, acoustically induced seizures of the DBA2 mice were not accompanied by cerebral prostanoid synthesis. This supports the view that the pathways involved in AS are different from those involved in PTZ or ES models of epilepsy.

Characterization of cysteinyl-leukotriene formation in primary astroglial cell cultures

The formation and composition of cysteinyl-leukotrienes (LT) in primary astroglial cell cultures prepared from newborn rat brain has been studied. Small amounts of cysteinyl-LT determined in terms of LTC4-like material in the supernatants of the cultures, became detectable after stimulation of the cells with 10(-5) M ionophore A23187. Cysteinyl-LT formation increased with time, reaching about 600 pg (mg protein)-1 after 60 min incubation. In contrast, considerable thromboxane (TX) B2 synthesis was found at 5 min following A23187-stimulation (about 30 ng TXB2 (mg protein)-1). The synthesis of cysteinyl-LT was abolished by 5 x 10(-5) M nordihydroguaiaretic acid (NDGA). Irrespective of the duration of incubation, blockage of prostanoid synthesis by 10(-6) M indomethacin did not result in increased cysteinyl-LT production. Reversed phase HPLC combined with radioimmunological detection showed that, after 60 min incubation in the presence of A23187, LTC4 and LTD4 accounted for practically all the LTC4-like immunoreactive material in the supernatants of cell cultures. No significant amounts of LTE4 could be detected. The results show that astrocytes may contribute to brain LTC4 and LTD4 synthesis. However, the cellular site of cerebral LTE4 formation seems to be other than the astroglia.

Formation and function of eicosanoids in the central nervous system

Neuronal firing during experimental convulsions triggered a large increase in brain eicosanoid synthesis. Mature astrocytes are an important source of cerebral prostanoids. Endogenously formed prostaglandins possess anticonvulsive properties of biological relevance. These conclusions suggest new ideas that might explain the formation and functions of prostanoids in the brain. First, as augmented neuronal discharge is a prerequisite for enhanced prostanoid synthesis during seizures, a functional coupling between firing neurons and prostanoid-forming astrocytes may be expected. Second, the anticonvulsive effects of endogenous prostanoids suggest that astroglia-derived substances might regulate neuronal activity. The phenomenon of convulsion-induced prostanoid synthesis may, therefore, represent a new example of neuron-glia interaction. Neither K+-induced membrane depolarization nor receptor activation by drugs with affinity to alpha or beta adrenoceptors, dopamine, serotonin, muscarine, histamine, GABA, glutamate, aspartate, adenosine, and opioid receptors evoked eicosanoid synthesis in astrocytes. The only physiologically relevant ligand that induced prostanoid synthesis concentration dependently in astrocytes was ATP and related nucleotide triphosphates, as well as nucleotide disphosphates. In peripheral nerves ATP serves as a cotransmitter. The effect of the P2 agonists was reduced by pertussis toxin. The mechanism by which eicosanoids regulate neuronal activity remains to be elucidated.

Multiple pertussis toxin substrates as candidates for regulatory G proteins of adenylate cyclase coupled to the somatostatin receptor in primary rat astrocytes

The involvement of G proteins in receptor mediated astroglial cAMP formation was studied. Isoproterenol or prostaglandin E2 stimulated adenylate cyclase of primary astroglial cells was inhibited by somatostatin. Preincubation of cells with increasing concentrations of islet activating protein (IAP) diminished somatostatin inhibition of adenylate cyclase. At an IAP concentration of 50 ng/ml somatostatin inhibition was completely abolished. Studies on IAP catalyzed 32P-ADP-ribosylation of astroglial cell particulate material revealed an incorporation of radiolabel into three polypeptides in the molecular weight range of 41,000-39,000 Dalton. Pretreatment of intact cells with IAP reduced radiolabeling of this molecular species in a concentration dependent manner. No further radiolabeling above background level was detectable after pretreatment of cultures with 10 ng IAP/ml or more. At present, the occurrence of at least three IAP substrates (G proteins) does not permit an identification of the somatostatin receptor coupled G protein. Rather, the finding reveals that astrocytes are endowed with multiple variants of GTP binding proteins likely to be coupled to different receptors.

Characterization of seizure-induced cysteinyl-leukotriene formation in brain tissue of convulsion-prone gerbils

Tonic-clonic seizures elicited in convulsion-prone gerbils resulted in a large increase in immunoreactive prostaglandin (PG) F2 alpha and in a smaller increase in immunoreactive leukotriene (LT) C4-like material in brain tissue. Brain tissue contents of both eicosanoids were found to reach a maximum at 6 min after the onset of seizures and were still elevated at 54 min after the beginning of convulsions. By reversed phase HPLC the immunoreactive LTC4-like material was identified as LTC4 and LTD4 at 6 min after the onset of convulsions, whereas at 54 min after the onset, transformation of LTD4 to LTE4 could be detected as well. In gerbils showing only weak seizure activity a small increase in PGF2 alpha but no increase in immunoreactive LTC4-like material could be detected at 6 min after the onset of convulsions. Pretreatment with indomethacin abolished the formation of PGF2 alpha but significantly enhanced the biosynthesis of immunoreactive LTC4-like material at 18 min after the beginning of seizures. The results demonstrate formation of cysteinyl-LT following tonic-clonic convulsions in spontaneously convulsing gerbils which could be enhanced by inhibition of the cyclooxygenase pathway of arachidonic acid metabolism. Since cysteinyl-LT have potent biological actions in various organs this finding warrants further investigations on the potential role of cysteinyl-LT in the CNS.

The stable prostacyclin-analogue, iloprost, unlike prostanoids and leukotrienes, potently stimulates cyclic adenosine monophosphate synthesis of primary astroglial cell cultures

The effect of different eicosanoids on adenosine-3', 5'-cyclic-monophosphate (cAMP) accumulation in primary astroglial cell cultures prepared from newborn rat brain was studied. The stable prostacyclin-analogue, iloprost, effectively stimulated cAMP synthesis in a concentration-dependent, saturable manner, the EC50 being about 3 x 10(-8) M. Prostaglandin (PG) E2 was less potent, without reaching plateau even at 10(-5) M. Prostaglandins D2 and F2 alpha, and the stable thromboxane A2-analogue, U 46619, as well as leukotrienes (LT) B4, C4, D4 and E4 were not effective and did not attenuate basal or isoprenaline (10(-8) M)-stimulated astroglial cAMP formation. This is the first indication for the existence of a prostacyclin receptor coupled positively to the adenylate cyclase in astrocytes. Other eicosanoids are unlikely to be involved in receptor-mediated regulation of astroglial cAMP levels.

Effect of adjuvant reserpine treatment on catecholamine metabolism in schizophrenic patients under long-term neuroleptic treatment

The clinical and biochemical effects of adjuvant reserpine treatment were investigated in 12 chronic schizophrenic patients on long-term neuroleptic medication. The global severity of the symptoms using the Brief Psychiatric Rating Scale did not change significantly in the whole group, however, a moderate decrease in positive symptoms (factors though disturbance, activation and hostile-suspiciousness) was observed for 5 patients. Cerebrospinal fluid (CSF) noradrenaline levels showed a consistent decrease, but other biochemical parameters (CSF dopamine metabolites, platelet MAO and serum dopamine-beta-hydroxylase activities) did not change significantly. The changes of clinical symptoms and biochemical parameters did not show any correlation.

Are cerebral prostanoids of astroglial origin? Studies on the prostanoid forming system in developing rat brain and primary cultures of rat astrocytes

Prostanoid forming capacity in vitro and convulsion-induced prostanoid formation in vivo were studied in the developing rat brain. For comparison, prostanoid synthesis in homogenates of primary astrocyte cultures of different ages was also examined. There was no significant prostanoid production in homogenates from primary astrocyte cultures prepared one week after cultivation. Two-week-old astrocyte cultures possessed a prostanoid synthesizing system of high specific activity. The relative proportions of the products were similar to those obtained in brain homogenates of adult rats, prostaglandin D2 (PGD2) being the major product. Prostanoid forming capacity of brain homogenates was low at birth, increased during development and nearly reached adult values by day 21. Generalized convulsions could be evoked by pentylenetetrazol (PTZ) irrespective of age, but convulsion-induced prostanoid formation characteristic of adult rodents did not take place before the third week of postnatal life. The close similarities between the characteristic features of prostanoid synthesis in both brain and astroglial homogenates, together with the coincidence during brain development of the expression of cerebral prostanoid synthesis with the appearance of mature astrocytes suggest that astrocytes are an important source of brain prostanoids.

Formation of sulphidopeptide-leukotrienes in brain tissue of spontaneously convulsing gerbils

Five minutes after the onset of seizures high amounts of immunoreactive prostaglandin (PG) F2 alpha and smaller amounts of sulphidopeptide (SP)-leukotriene (LT)-like immunoreactivity could be detected in gerbil brain tissue. Bilateral carotid artery ligation followed by 15 min of reperfusion even more enhanced brain tissue contents of PGF2 alpha and SP-LT-like material. Analysis of the immunoreactive SP-LT-like material by reversed phase high pressure liquid chromatography (h.p.l.c.) revealed immunoreactivity co-eluting with authentic LTC4 and LTD4.

Synthesis and pharmacological evaluation of some new tetrahydroisoquinoline derivatives inhibiting dopamine uptake and/or possessing a dopaminomimetic property

As shown by structure-activity relationship studies in 8-(substituted-amino)-4-aryl-2-methyl-1,2,3,4-tetrahydroisoquinolines, the most important structural requirement for a marked antidepressant action is the presence of an ureido, (alkoxycarbonyl)amino, or [(alkylamino)acyl]amino group attached to the isoquinoline skeleton in position 8. In one of the biological tests a significant difference was found between 8-amino-4-phenyl-2-methyl-1,2,3,4-tetrahydroisoquinoline (nomifensine) and the new compounds synthesized. Nearly all compounds substituted in the amino group either decrease the spontaneous motility in mice or exert no effect on it. Two syntheses have been elaborated for the preparation of the compounds represented by the general formulas II-V where R1 = hydrogen, halogen, or methyl; Y = CONHR, OCOR, or CO(CH2)nNHR, in which R = alkyl or aralkyl or NHR = cyclic amine and n = 1-2. The syntheses start either from the corresponding 8-amino-4-aryl-2-methyl-1,2,3,4-tetrahydroisoquinolines or from the corresponding noncyclized amino alcohols. Of the compounds, 4-(p-chlorophenyl)-8-[(ethoxy-carbonyl)amino]-2-methyl-1,2,3,4- tetrahydroisoquinoline was found to possess the highest activity.

The formation and regional distribution of prostaglandins D2 and F2 alpha in the brain of spontaneously convulsing gerbils

The distribution of the two major cyclooxygenase products prostaglandin D2 (PGD2) and prostaglandin F2 alpha (PGF2 alpha) in 7 different regions of the brain (medulla, cerebellum, hypothalamus, striatum, midbrain, hippocampus and cerebral cortex) was studied. Basal levels were highest in hypothalamus and cortex. Following convulsions elicited by environmental stress prostaglandin concentrations increased in all areas, with largest increases (10-20-fold) in hippocampus and cortex, reaching 70 ng/g PGD2 in hippocampus and 115 ng/g PGD2 in cortex. These results demonstrate that, during spontaneous seizures, there is a greater increase in prostanoid production in those areas involved in the convulsive process.

Decreased levels of brain cyclo-oxygenase products as a possible cause of increased seizure susceptibility in convulsion-prone gerbils

Basal levels of 5 cerebral prostanoids (PGD2, PGF2 alpha, PGE2, 6-keto-PGF1 alpha and thromboxane/TX/B2) were measured radioimmunologically in normal and convulsion-prone gerbils. Significantly less PGD2,PGE2 and 6-keto-PGF1 alpha was found in the brain of seizure-sensitive animals. After treatment with indomethacin, which reduced the amount of brain cyclo-oxygenase products, also normal gerbils exhibited convulsions following environmental stress. The results are in accordance with the hypothesis that endogenous prostanoids play a role in the regulation of seizure susceptibility.

Anticonvulsive effects of endogenous prostaglandins formed in brain of spontaneously convulsing gerbils

Seizures were induced in a strain of epileptic gerbils by moderate environmental stress. Concentrations of five different cyclooxygenase products (PGD2, PGF2 alpha, PGE2, 6-keto-PGF1 alpha and thromboxane B2) were measured in brain by specific radioimmunoassays before and at different time intervals after the onset of clonic-tonic convulsions. All prostanoids markedly increased subsequent to the convulsions. Maximal concentrations were reached after about 15 min. The major compound detected was PGD2, followed by PGF2 alpha and lower concentrations of the other cyclooxygenase products. Indomethacin completely prevented the convulsion-induced formation of prostanoids. Fifteen min after a first seizure almost all animals proved to be protected against a second convulsion. Indomethacin pretreatment markedly reduced the number of convulsion-resistant animals. These findings are compatible with the hypothesis that endogenous prostaglandins exert anticonvulsive effects.

Changes in cyclooxygenase activity and prostaglandin profiles during monoamine metabolism in rat brain homogenates

The effect of different monoamine oxidase (MAO) substrates on the endogenous prostaglandin(PG) and thromboxane (TX) biosynthesis in rat brain homogenates was studied. In the absence of MAO substrates the following pattern of arachidonic acid metabolites was found: PGD2 greater than PGF2 alpha greater than TXB2 greater than PGE2 greater than or equal to 6ketoPGF1 alpha. Phenylethylamine(PEA) stimulated the cyclooxygenase activity 1.5-fold (expressed as the sum of the products formed), without altering the product profile. Tyrosine(Tyr) caused a twofold increase in cyclooxygenase activity and slightly modified the product composition (PGD2=PGF2 alpha greater than PGE2 greater than TXB2 greater than 6ketoPGF1 alpha). In the presence of noradrenaline(NA) there was a threefold stimulation of cyclooxygenase activity. The increase of PGF2 alpha was more pronounced than that of the other metabolites (PGF2 alpha greater than PGD2 greater than TXB2 greater than PGE2 greater than 6ketoPGF1 alpha). alpha-Methylnoradrenaline(alpha metNA ) (not a substrate for MAO but bearing the catechol group) altered the PG pattern in the same way as NA, but without enhancing the cyclooxygenase activity. PEA or Tyr when administered together with alpha metNA produced a NA-like effect both on the cyclooxygenase activity and on the product profile. The increase in cyclooxygenase activity was abolished by pargyline or by catalase, independently of the activator system used. The results support the hypothesis that NA-stimulation of brain PG (and TX) formation is mediated by H2O2 formed during the degradation of the amine via MAO. The role of the catechol group in protection of the cyclooxygenase against inactivation and in the changes of product composition, as well as the possible significance of the coupling between arachidonate and monoamine metabolism is discussed.

Evidence for the localization of hydrogen peroxide-stimulated cyclooxygenase activity in rat brain mitochondria: a possible coupling with monoamine oxidase

The distribution of basal and of H2O2-stimulated cyclooxygenase activity in the primary fractions of rat brain homogenates and in the subfractions of crude mitochondrial fraction was studied. For comparison, the localization of H2O2-generating monoamine oxidase (MAO) as well as that of the mitochondrial marker succinate dehydrogenase (SDH) was also examined. H2O2 was generated by MAO using 5 x 10(-4) M noradrenaline (NA) or 2 x 10(-4) M 2-phenylethylamine (PEA) as substrates, or by 25 micrograms glucose oxidase (GOD) per ml in the presence of 1 mM glucose. For nonstimulated (basal) cyclooxygenase, the relative specific activity (RSA) was high in microsomes (1.79) and in the free mitochondria-containing subfraction of the crude mitochondrial fraction (1.94). Parallel distribution of MAO and H2O2-stimulated cyclooxygenase was observed in all fractions studied in the presence of NA. The highest RSA was found in the purified mitochondria for both enzymes (1.85 for MAO and 1.97 for H2O2-stimulated cyclooxygenase). The enrichment of SDH (RSA = 2.21) indicated a high concentration of mitochondria in this fraction. The same distribution of H2O2-stimulated cyclooxygenase was obtained when, instead of the MAO-NA system, hydrogen peroxide was generated by GOD in the presence of glucose. H2O2 generated by deamination of NA or PEA by MAO, or during the enzymatic oxidation of glucose by GOD, caused a threefold increase in mitochondrial endoperoxide formation. Indomethacin (2 x 10(-4) M), catalase (50 micrograms/ml), and pargyline (2 x 10(-4) M) eliminated the MAO-dependent mitochondrial synthesis of PG endoperoxides. The GOD-dependent cyclooxygenase activity in this fraction was abolished by indomethacin or catalase, but not by pargyline. The results show the existence of a mitochondrial cyclooxygenase in brain tissue. The enzyme is sensitive to H2O2 and produces prostaglandin endoperoxides from an endogenous source of arachidonic acid. The identical localization of H2O2-producing MAO and H2O2-sensitive cyclooxygenase suggests a possible coupling between monoamine and arachidonic acid metabolism.

Receptor independent stimulatory effect of noradrenaline on Na,K-ATPase in rat brain homogenate. Role of lipid peroxidation

The effect of different adrenoceptor agonists on Na,K-ATPase activity and lipid peroxidation of rat brain homogenate was studied. Drugs which enhanced Na,K-ATPase activity--noradrenaline, adrenaline and oxymethazoline--were found to inhibit endogenous membrane lipid peroxidation. Other drugs--phenylephrine, xylazine and clonidine--which did not cause any change in the enzyme activity did not influence lipid peroxidation either. No increase of Na,K-ATPase activity by noradrenaline could be detected after preincubation of the homogenate for 5 min at 37 degrees. During this time endogenous lipid peroxidation of considerable extent could be observed. It is concluded that there is no correlation between the adrenoceptor agonist feature of noradrenaline and its stimulatory effect on Na,K-ATPase activity of rat brain homogenate. However, it seems likely that in rat brain homogenate the increase of Na,K-ATPase activity and inhibition of endogenous lipid peroxidation by noradrenaline are related.

On the mechanism of the involvement of monoamine oxidase in catecholamine-stimulated prostaglandin biosynthesis in particulate fraction of rat brain homogenates: role of hydrogen peroxide

The mechanism of involvement of monoamine oxidase (MAO) in catecholamine-stimulated prostaglandin (PG) biosynthesis was studied in the particulate fraction of rat brain homogenates. High concentrations of either noradrenaline (NA) or dopamine (DA) stimulated effectively PGF2 alpha formation. The same amount of 2-phenylethylamine (PEA) acted similarly, provided that it was administered together with a catecholamine analogue or metabolite possessing the 3,4-dihydroxyphenyl nucleus--3,4-dihydroxyphenylalanine (DOPA), 3,4-dihydroxyphenylacetic acid (DOPAC), 3,4-dihydroxyphenylglycol (DOPEG), 3,4-dihydroxyphenylacetaldehyde (DOPAL), or alpha-methylnoradrenaline (alpha-met-NA)--or with SnCl2. In the absence of PEA, these compounds were ineffective with regard to stimulation of PGF2 alpha formation. Catalase, pargyline, or indomethacin abolished completely PGF2 alpha formation elicited either by catecholamines or by PEA plus a 3,4-dihydroxyphenyl compound or SnCl2. With regard to the stimulation of PGF2 alpha formation in the presence of alpha-met-NA, PEA could be replaced by H2O2 generated by the glucose oxidase(GOD)-glucose system. The effect of H2O2 was inhibited by indomethacin or catalase, but pargyline was ineffective. It is assumed that catecholamines play a dual role in the activation of PG biosynthesis in brain tissue. During the enzymatic decomposition of catecholamines MAO produces H2O2, which stimulates endoperoxide synthesis. Simultaneously, catecholamines as hydrogen donors promote the nonenzymatic transformation of endoperoxides into PGF2 alpha. The possible physiological importance of these findings is discussed.

Studies on prostaglandin F2 alpha formation caused by pentametylenetetrazol-induced convulsions in rat brain

Prostaglandin F2 alpha formation caused by pentametylenetetrazol convulsions was studied as a function of the duration, the doses of the convulsant and the intensity of the seizures. It was shown by the statistical analysis of the results in the case of clonic convulsions that the amount of synthetized PGF2 alpha did not depend on the doses of convulsant, while close relation existed between the duration and the PGF2 alpha production. At the same time, during tonic convulsions lasting longer than 50 sec, no more increase in the PGF2 alpha content of the brain was observed. An experimental model is suggested to study in vivo the mechanisms regulating the brain's prostaglandin biosynthesis. Pretreatment of the animals with reserpine did not affect the rate of convulsion-induced PGF2 alpha-formation.

Protective role of brain ascorbic acid content against lipid peroxidation

The high ascorbic acid concentration in the brain inhibits lipid peroxidation induced by various agents in rat brain microsomes. The physiological importance of the fact is discussed.