Selective antagonism of native and cloned kainate and NMDA receptors by polyamine-containing toxins

Antagonism of rat excitatory amino acid receptors by a synthetic analog [philanthotoxin-343 (PhTX-343)] of a polyamine amide, wasp toxin (philanthotoxin-433) and a structurally related spider toxin, argiotoxin-636 (ArgTX-636), was examined in Xenopus oocytes injected with rat brain RNA or RNA transcribed from the excitatory amino acid receptor clones GluR1, GluR2 and NMDAR1. Antagonism of both kainate- and N-methyl-D-aspartate (NMDA)-elicited responses by PhTX-343 and ArgTX-636 was reversible, noncompetitive and partly voltage-dependent. Dose-inhibition curves were constructed using EC50 concentrations of kainate (100 microM) and N-methyl-D-aspartate (33 microM) in the presence of variable concentrations of ArgTX-636 and PhTX-343. In oocytes injected with rat brain RNA, IC50s for antagonism of kainate-induced currents were similar, i.e., 0.07 microM and 0.12 microM for ArgTX-636 and PhTX-343, respectively, whereas IC50s for antagonism of NMDA-induced currents were dissimilar, i.e., 0.04 microM for ArgTX-636 and 2.5 microM for PhTX-343. In oocytes expressing NMDAR1, IC50s were similar to those for the antagonism of NMDA-induced currents of oocytes injected with rat brain RNA. PhTX-343 and ArgTX-636 were more or less equally potent (IC50s were 2.8 microM and 3.4 microM, respectively) antagonists of the response of GluR1 to 100 microM kainate. However, GluR1 was approximately 50 times less sensitive to the toxins than non-N-methyl-D-aspartate receptors expressed in oocytes injected with rat brain RNA. Receptors co-expressed from GluR1 + GluR2 were virtually insensitive to PhTX-343 (IC50 = 270 microM) and to ArgTX-343 (IC50 approximately 300 microM).

Species-specific induction of cytochrome P-450 4A RNAs: PCR cloning of partial guinea-pig, human and mouse CYP4A cDNAs

PCR was used to demonstrate the presence of a conserved region and to clone novel members of the cytochrome P-450 4A gene family from guinea pig, human and mouse cDNAs. This strategy is based on the sequences at nucleotides 925-959 and at the haem binding domain (nucleotides 1381-1410) of the rat CYP4A1 gene. Murine Cyp4a clones showed high sequence identity with members of the rat gene family, but CYP4A clones from human and guinea pig were equally similar to the rat/mouse genes, suggesting that the rat/mouse line had undergone gene duplication events after divergence from human and guinea-pig lines. The mouse Cyp4a-12 clone was localized to chromosome 4 using interspecific backcross mapping, in a region of synteny with human chromosome 1. The assignment of the human CYP4A11 gene to chromosome 1 was confirmed by somatic cell hybridization. An RNAase protection assay was shown to discriminate between the murine Cyp4a-10 and Cyp4a-12 cDNAs. Treatment of mice with the potent peroxisome proliferator methylclofenapate (25 mg/kg) induced Cyp4a-10 RNA in liver, and to a lesser extent in kidney; there was no sex difference in this response. Cyp4a-12 RNA was present at high levels in male control liver and kidney samples, and was not induced by treatment with methylclofenapate. However, Cyp4a-12 RNA was present at low levels in control female liver and kidney RNA, and was greatly induced in both organs by methylclofenapate. Guinea pigs were exposed to methylclofenapate (50 mg/kg), but there was no significant induction of the guinea-pig CYP4A13 RNA. These findings are consistent with a species difference in response to peroxisome proliferators between the rat/mouse and the guinea pig.

Induction of cytochrome P450 and peroxisomal enzymes by clofibric acid in vivo and in vitro

We have analysed the induction of microsomal and peroxisomal proteins and their RNAs after treatment of hepatocytes with the peroxisome proliferator, clofibric acid, in vitro and in vivo. After treatment of hepatocytes with 1 mM clofibric acid for 4 days, P450 4A1 RNA is induced 500-fold, and acyl-CoA oxidase and P450 2B1 280-fold, relative to control cultures. These RNAs are detectably induced after administration of 25 microM clofibric acid, and show a similar induction response with increasing doses of clofibric acid. Western blot analysis of the P450 4A and bifunctional enzyme (BFE) proteins showed that both were induced in parallel with increasing doses of clofibric acid, over a range of 25 microM-1 mM. The distribution of the induced proteins was examined by immunocytochemistry. Increasing doses of clofibric acid led to an increase in the average intensity of staining for both proteins throughout the hepatocyte population. There was, however, a graded variation between hepatocytes in the intensity of staining, both for P450 4A and BFE proteins. The heterogeneity in response of the hepatocyte population in vitro may be related to differential sensitivity of hepatocytes to induction in vivo. Therefore, rats were dosed with 0, 50 or 300 mg/kg of clofibric acid for 4 days by gavage, and the livers were examined by immunocytochemistry. After 50 mg/kg of clofibric acid, both P450 4A and BFE were induced mainly in zones 3 and 2 of the liver acinus. However, after 300 mg/kg of clofibric acid, staining for both proteins was strong and homogenous throughout the liver acinus. Thus, hepatocytes from zones 3 and 2 of the acinus are differentially responsive to induction by clofibric acid.

Transvascular albumin flux in rabbit hindlimb after tourniquet ischemia

Transvascular clearance of labeled rabbit albumin was measured in gastrocnemius muscle and heel skin from anesthetized rabbits after 1 or 2 h of tourniquet ischemia. Albumin clearance, calculated as a 1-h extravascular uptake, was 4.7 +/- 0.4 and 29 +/- 1 microliter.h-1 x g dry wt-1 for control gastrocnemius muscle and heel skin, respectively. During the first hour of reperfusion, the clearance was 101 +/- 23 and 56 +/- 6 microliters.h-1 x g dry wt-1 in the muscle and skin, respectively. The clearance in skin during the second and third hour of reperfusion was not different from control. The increased clearance in muscle persisted during 2 h of reperfusion but returned to control levels during the third hour of reperfusion. The solvent drag reflection coefficient was measured by increasing venous pressure during reperfusion in one leg after bilateral ischemia. In skin, the reflection coefficient, calculated as 1 minus the change in clearance divided by the change in water weight, was 0.94 +/- 0.05 and did not change with tourniquet ischemia. The reflection coefficient in muscle was 0.98 +/- 0.01 for control animals and decreased to 0.66 +/- 0.11 during the first hour of reperfusion. The reflection coefficient was not different from control during the third hour of reperfusion. The transitory increase in microvascular permeability to albumin in skeletal muscle is more indicative of an acute inflammatory response than of endothelial injury.

Albendazole is effective treatment for chronic strongyloidiasis

A total of 301 British ex-Far East prisoners of war, many of whom worked on the Thai-Burma Railway during World War II, consecutively attended The Liverpool School of Tropical Medicine for clinical review between January 1987 and August 1990. Fifty-two (17%) were found to have chronic strongyloidiasis. Diagnostic criteria included any of the following: characteristic larva currens rash, positive Strongyloides serology, and positive stool examination. Forty-seven were evaluable 6 months, after therapy with albendazole 400 mg twice daily for 3 days, which resulted in a 75% cure rate. Cure was defined as disappearance of the rash, if present, negative serology and negative stool examination. Patients who had more than one positive diagnostic feature were only considered cured if both or all had disappeared or become negative. All 12 of the patients in whom initial treatment failed were given a second course of albendazole: three further cures were obtained in eight evaluable patients. The overall cure rate was 81%. The only side-effects recorded were mild nausea and diarrhoea in one patient. We suggest that albendazole should be the treatment of choice for chronic strongyloidiasis.

Vascular smooth muscle responses to endothelial autacoids in rats with chronic coarctation hypertension

OBJECTIVE

To examine whether elevated intravascular pressure in chronic hypertension alters responses of vascular smooth muscle to agents of endothelial origin.

METHODS

Coarctation hypertensive, sham normotensive control, and one-kidney, one clip hypertensive (1K1C) rats were used. Tail systolic, carotid and femoral arterial pressures were measured. Responses to histamine, endothelin-1 and the prostacyclin analog iloprost were evaluated in isolated helically cut strips of thoracic and abdominal aortas, with and without endothelium, from all groups. Responses to nitroglycerin were also evaluated in strips of abdominal aortas.

RESULTS

Thoracic aortas from 1K1C and coarctation hypertensive rats, as well as abdominal aortas from 1K1C rats, but not abdominal aortas from coarctation hypertensive rats were exposed chronically to elevated arterial pressure. Endothelium-dependent maximal relaxation by histamine was significantly depressed in thoracic aortas from both groups of rats, as well as in abdominal aortas from 1K1C rats. Maximal relaxation and sensitivity to histamine were normal in abdominal aortas from coarctation hypertensive rats. Sensitivity to nitroglycerin was impaired in abdominal aortas from 1K1C rats but not in those from coarctation hypertensive rats; maximal relaxation to nitroglycerin was similar in all groups. Relaxation to iloprost was independent of the endothelium, observed only in thoracic aortas and impaired in hypertensive rats. Responses to endothelin-1 were similar in the groups.

CONCLUSION

Vasorelaxation by histamine, iloprost and nitroglycerin are impaired in hypertension. The impaired relaxation by histamine results from exposure of the vascular endothelium to chronically elevated pressure. This impairment may be related to effects of high pressure in reducing the ability of the endothelium to produce endothelium-derived relaxing factor and inhibit cyclic GMP-dilator mechanisms.

Simultaneous measurement of fluid and protein permeability in isolated rabbit lungs during edema

Fluid conductance and protein permeability have been studied in isolated perfused lung models of pulmonary edema. However, previous studies have not investigated changes of both fluid conductance and protein permeability in the same isolated lung preparation after injury. Arachidonic acid (AA) metabolites are involved in the inflammatory processes that lead to the development of pulmonary edema. The hemodynamic effects of AA have been well established; however, controversy exists concerning the ability of AA to alter the permeability of the pulmonary microvasculature to fluid and protein. The purpose of this study was to simultaneously determine whether transvascular fluid conductance and protein permeability are increased in isolated perfused rabbit lungs with pulmonary edema induced by AA. Indomethacin (80 microM) was added to the perfusate to inhibit the hemodynamic effects of AA and produce a pressure-independent model of pulmonary edema. Fluid conductance was assessed by determination of the capillary filtration coefficient (Kf), and protein permeability was evaluated by measurement of 125I-albumin clearance. The injection of AA (3 mg/200 ml of perfusate) into the pulmonary arterial catheter resulted in an increase in lung weight over the remaining 30-min experimental period. Kf (microliter.s-1 x cmH2O-1 x g dry lung-1) was increased (P < 0.05) in AA-treated lungs at 10 and 30 min post-AA injection when compared with control lungs and baseline values (determined 10 min before AA injection). Albumin clearance was also greater (P < 0.05) in lungs that received AA. 125I-albumin clearance was measured at different rates of fluid flux produced by elevation of venous pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Transvascular albumin and IgG flux in skin and skeletal muscle following plasmapheresis

The extravascular uptake for labeled albumin and IgG and the extravascular masses for endogenous albumin and IgG were measured in skin and skeletal muscle from anesthetized rabbits following 24 hr of intermittent plasmapheresis. An amount of protein equivalent to the total intravascular protein mass was removed. There was a significant reduction in the extravascular mass for albumin in both tissues and for IgG in skin. The shift of albumin out of the extravascular space of skin and skeletal muscle could account for 95% of the vascular replacement of albumin. The extravascular uptake for the labeled proteins was measured as the 1-hr extravascular distribution space at plasma concentration divided by time and expressed as a plasma clearance. The plasma volume in the tissue samples was estimated from the 3-min distribution space for labeled transferrin. Following plasmapheresis the rate of extravascular uptake for both labeled proteins was greater than that for control or sham-operated animals, suggesting an increase in transvascular protein permeability. The transvascular fluxes for native albumin and IgG were not increased due to the decrease in the plasma concentrations. The results were consistent with the major mechanism for a shift of plasma proteins being due to a decrease in plasma protein concentration and a subsequent increase in lymph flow instead of a decrease in transvascular protein permeability.

Permeability changes following ischemia-reperfusion injury in the rabbit hindlimb

Changes in permeability following ischemia-reperfusion injury were assessed in the intact rabbit hindlimb by measuring the transvascular clearance of 125I-labeled rabbit serum albumin. Ischemia was induced for periods of 1 or 2 hours by use of a pneumatic tourniquet inflated to 300 mmHg. Following ischemia, the limb was reperfused for 1, 2, or 3 hours. The albumin clearance in the gastrocnemius muscle of control rabbits was 5.1 +/- 0.7 (mean +/- SEM) microliters/hr/g dry weight. Following 1 hour of ischemia and reperfusion, muscle albumin clearance rose to 71.4 +/- 26 microliters/hr/g dry weight which was not significantly different from those animals that underwent 2 hours of ischemia. Muscle albumin clearance continued to be elevated following 2 hours of reperfusion; however, it returned toward control levels after 3 hours of reperfusion. These data suggest there is a transient increase in albumin permeability following ischemia-reperfusion injury in skeletal muscle.

Transvascular albumin and IgG flux in skin after a continuous 3-h bradykinin infusion

Bradykinin (1 microgram/min) was infused into the femoral artery of one hindleg of anesthetized rabbits for 3 h. Measurements of the initial extravascular uptake for labeled albumin and immunoglobulin (Ig) G were compared with measurements of the lymph protein flux for endogenous albumin and IgG. With bradykinin, the initial extravascular uptake for both albumin and IgG, calculated as the 1-h extravascular distribution space at plasma concentration divided by time and expressed as a plasma clearance, was 12 times the control values. For both proteins, the lymph fluxes were not significantly greater than the values for extravascular uptake, indicating that the sustained increase in lymph protein flux was not due to washout of interstitial protein. The extravascular uptake for IgG was approximately 80% of that for albumin in both control and bradykinin animals, suggesting that the sustained response did not change the selectivity between the two proteins. Changes in the extravascular masses of endogenous albumin and IgG suggest that the initial response to bradykinin was a transient formation of endothelial gaps that did not restrict transvascular IgG transport more than albumin.

Comparison of protein lymph flux and extravascular uptake in skin during increased venous pressure

The hypothesis that the albumin reflection coefficient is underestimated from measurements of lymph protein flux because of a prolonged interstitial washout was tested in the hindleg of anesthetized rabbits. In heel skin, the initial extravascular uptake for labeled albumin and immunoglobulin G (IgG) was compared with prenodal lymph flux for native albumin and IgG. Venous pressure was increased in one leg for 4 h, while the contralateral leg was the control. The extravascular uptake for labeled albumin was 67% greater than control during the fourth hour of increased venous pressure. Lymph albumin flux was 2.3 times control, indicating a small but significant washout of interstitial albumin. The magnitude of the interstitial washout for IgG was less than that for albumin. Using the relationship between the change in extravascular uptake and the change in lymph flow, the reflection coefficients for albumin and IgG were both 0.91. The reflection coefficient for albumin using lymph protein flux was lower because of a continued interstitial washout.

Differential tissue-specific expression and induction of cytochrome P450IVA1 and acyl-CoA oxidase

We have examined the tissue-specific expression and inducibility of acyl-CoA oxidase and cytochrome P450IVA1 (P450IVA1) RNA in rats. Groups of three rats were dosed daily by gavage with methylclofenapate at 25 mg/kg in 5 ml/kg corn oil for nine weeks, or were administered a vehicle control. P450IVA1 and acyl-CoA oxidase RNA were detected using an RNase protection assay. Similar levels of acyl-CoA oxidase RNA were present in control liver and kidney, but the level of this RNA in lung, muscle and testis was 6-11%, and in pancreas was 0.13%, of that in liver. Treatment of rats with methylclofenapate led to an 11-fold induction of acyl-CoA oxidase RNA in liver and also produced a significant induction of this RNA in kidney, lung, muscle and testis of 1.7-fold, 1.3-fold, 2-fold and 1.7-fold, respectively. Acyl-CoA oxidase RNA was not induced in pancreas. P450IVA1 RNA was present in control liver and also in kidney of control rats at 28% of the level in liver. In contrast to acyl-CoA oxidase RNA, P450IVA1 RNA was not detected in lung, pancreas or testis. Methylclofenapate treatment of rats led to an 18-fold induction of P450IVA1 RNA in liver, and a sevenfold induction in kidney. Induction of P450IVA1 was not detected in any of the other tissues examined. Quantification of the relative amounts of acyl-CoA oxidase and P450IVA1 RNA in control liver revealed that acyl-CoA oxidase RNA was present in a 17.5-fold molar excess over P450IVA1 RNA. Western blotting with an anti-P450IVA IgG revealed two bands of similar apparent molecular mass in liver and kidney microsomes, but not in microsomes from the testis of control rats. Methylclofenapate treatment of rats caused an increase in the intensity of these bands in microsomes from liver, but no induction was obvious in kidney. Immunocytochemical staining for both the microsomal P450IVA and peroxisomal acyl-CoA oxidase proteins was restricted to the proximal convoluted tubule in the kidney cortex, with staining being most intense in the S3 region.

Importance of charge on transvascular albumin transport in skin and skeletal muscle

To test the hypothesis that charge affects the transvascular transport of albumin, the tracer clearance for albumin and a set of charge-modified albumins was measured in heel skin and gastrocnemius muscle from anesthetized rabbits. The charge on albumin was made less negative by modifying the carboxyl groups of aspartic and glutamic acids to alcohol groups. Four preparations of modified albumin having isoelectric points of 5.1 +/- 0.4, 5.8 +/- 0.4, 7.1 +/- 0.5, and 8.1 +/- 0.7 were studied. In skin, the clearances for the most neutral modified albumin and cationic albumin were 20 and 80% greater than that for native albumin, respectively. In skeletal muscle, the clearances for the most neutral modified albumin and cationic albumin were 50% and 1.5 times greater than that for native albumin, respectively. Calculation of the reflection coefficient for native albumin from the change in clearance with increased venous pressure resulted in estimates greater than 0.95 in both tissues. The change in clearance for the modified albumins during increased venous pressure was not different from that for native albumin. Charge appears to effect transvascular diffusion of proteins more than convective transport.

Zone-specific inducibility of cytochrome P450 2B1/2 is retained in isolated perivenous hepatocytes

The expression and induction of the cytochrome P450 2B1/2 isoenzyme is heterogeneous, exhibiting a regional pattern in the intact liver and a varied response to phenobarbital in isolated cultured hepatocytes. We report that P450 2B1/2 immunostaining of hepatocytes isolated from the perivenous liver region and cultured in the presence of phenobarbital is much stronger than that of cells identically treated but isolated from the periportal region. P450 2B1 mRNA, quantified by a sensitive and specific RNAase protection assay, is also preferentially induced in perivenous hepatocytes, demonstrating that the difference in induced expression is at the pretranslational level. Our results suggest that perivenous and periportal hepatocytes are differentially imprinted to retain regiospecific factors governing their inducibility after isolation.

Water in Earth's Mantle: The Role of Nominally Anhydrous Minerals

Most minerals of Earth's upper mantle contain small amounts of hydrogen, structurally bound as hydroxyl (OH). The OH concentration in each mineral species is variable, in some cases reflecting the geological environment of mineral formation. Of the major mantle minerals, pyroxenes are the most hydrous, typically containing approximately 200 to 500 parts per million H(2)O by weight, and probably dominate the water budget and hydrogen geochemistry of mantle rocks that do not contain a hydrous phase. Garnets and olivines commonly contain approximately 1 to 50 parts per million. Nominally anhydrous minerals constitute a significant reservoir for mantle hydrogen, possibly accommodating all water in the depleted mantle and providing a possible mechanism to recycle water from Earth's surface into the deep mantle.

Influence of saline infusions on transvascular protein transport

Anesthetized rabbits were given an intravenous infusion of saline over a 1-h period to increase transvascular protein transport in skin and skeletal muscle. The infusion rate was adjusted to rapidly decrease the plasma concentration of total protein without increasing mean arterial blood pressure or the venous pressure in the leg. The 1-h clearance for radiolabeled albumin and a set of charge-modified albumins was measured in the heel skin and the gastrocnemius muscle. For both skin and skeletal muscle, the clearance for native albumin during the saline infusion was twice the value for control. The increase in clearance for the most neutral protein was greater than that for native albumin, suggesting that transvascular fluid movement was through a pathway which excludes native albumin. The clearance for cationic albumin increased slightly in skin and did not change in skeletal muscle, indicating that transport of the cationic protein through this pathway is predominantly diffusion. The data were consistent with a two-pore model for transvascular transport of water and proteins and with the increase in water transport through the small pores during the saline infusion.

Induction of acyl-CoA oxidase and cytochrome P450IVA1 RNA in rat primary hepatocyte culture by peroxisome proliferators

We have characterized the induction of acyl-CoA oxidase and cytochrome P450IVA1 RNAs in a primary hepatocyte culture system in vitro, using a sensitive and specific RNAse protection assay. Hepatocytes were cultured with a maximal inducing dose of the peroxisome proliferator clofibric acid (1 mM), or vehicle control, for 4 days, and the level of RNAs compared with the level in rats which had been treated with corn oil or clofibric acid (300 mg/kg) for 4 days. The level of acyl-CoA oxidase and P450IVA1 RNAs in 4-day-old control hepatocytes was less than 2% of that in control liver. However, the level of these RNAs in RNA from treated hepatocytes was 61% of that in liver RNA from treated rats. Hepatocytes were treated with the potent peroxisome proliferator methylclofenapate (100 microM), and the induction of RNAs determined at various times after exposure. P450IVA1 RNA was significantly induced 1 h after dosing, rising to 34-fold above control after 8 h, whereas acyl-CoA oxidase RNA was not significantly induced until 4 h, increasing to 5.2-fold above control after 8 h. A similar time course of induction was seen after treatment of hepatocytes with 100 microM-nafenopin, 100 microM-methylclofenapate, 1 mM-clofibric acid or 1 mM-mono(ethylhexyl) phthalate, suggesting that the differential time course of induction of P450IVA1 and acyl-CoA oxidase RNAs is not related to the esterification, structure or potency of the peroxisome proliferator, but is intrinsic to the process of peroxisome proliferation. Hepatocytes were treated with methylclofenapate in the presence and absence of cycloheximide. P450IVA1 RNA was significantly induced by methylclofenapate in the presence of cycloheximide, rising to 17-fold above control after 8 h. However, no induction of acyl-CoA oxidase RNA was detected in the presence of cycloheximide. Therefore we characterize the induction of acyl-CoA oxidase and P450IVA1 RNAs in primary hepatocyte culture in vitro as a faithful model of the induction response in rat liver, and suggest that induction of P450IVA1 RNA is a primary event in the process of peroxisome proliferation.

Regulation of differentially spliced transcripts of acyl-CoA oxidase in the rat

RNAse protection assay was used to distinguish between and to quantify alternatively spliced transcripts of acyl-CoA oxidase in liver, kidney and testis of control and methylclofenapate treated rats. The ratio of spliced transcripts (type I to II) was 1.18:1 in control liver RNA, with 130 and 110 molecules/cell, respectively, and 3.1:1 in treated liver RNA, with 2800 and 900 molecules/cell. The ratios were 1.6 and 2:1 in control and treated kidney, and 0.31:1 in testis. This is likely to be due to differential splicing, which is, therefore, regulated during peroxisome proliferation, and also in a tissue specific fashion.

Effect of fluid resuscitation from endotoxin shock on lung transvascular fluid and protein exchange

The hypothesis that volume expansion during septic shock produces a greater transvascular protein flux than volume expansion alone was tested in anesthetized sheep by giving a high dose of endotoxin (40 micrograms/kg) intravenously. After 0.5 h of systemic hypotension, Ringer lactate, equivalent to 8% body wt, was infused followed by an additional 4 h of lymph collection. The results were compared with those from control animals receiving only Ringer lactate. The changes in plasma total protein with time were similar between groups. The increases in lymph flow and lymph protein flux were greater in the endotoxin-challenged group compared with the control group receiving Ringer lactate during the first 2 h but were similar thereafter. The interstitial volume was greater in the endotoxin-challenged animals compared with controls. The extravascular masses or apparent tissue concentrations for albumin or immunoglobulin G did not change in either group receiving Ringer lactate. The pulmonary edema following resuscitation from septic shock with Ringer lactate could be accounted for by either the pulmonary hypertensive effects of endotoxin or an initial, transient increase in microvascular protein permeability but not a sustained increase in microvascular permeability.

Localization and differential induction of cytochrome P450IVA and acyl-CoA oxidase in rat liver

The peroxisome proliferators are structurally diverse chemicals which induce hyperplasia, hypertrophy and the proliferation of peroxisomes in the rodent liver. Cytochrome P450IVA1 and peroxisomal enzymes, such as acyl-CoA oxidase, are induced and are early markers of treatment with peroxisome proliferators. In this study, rats were dosed intraperitoneally with the potent peroxisome proliferator methylclofenapate and the hepatic induction response was studied. There was no significant change in the enzyme activities of laurate hydroxylase (cytochrome P450IVA1) or acyl-CoA oxidase in the first 8 h after treatment, but the activities had doubled at 24 h, suggesting that these enzymes are not involved in the mediation of early events in peroxisome proliferation. Hepatic cytochrome P450IVA1 mRNA was significantly increased at 6 and 8 h after treatment, rising to 15-fold above control values at 30 h. In contrast, acyl-CoA oxidase mRNA showed no significant change in the first 8 h, but increased to 13-fold above control values at 24 and 30 h, thereby demonstrating different kinetics of induction of the two mRNAs. In order to determine whether cytochrome P450IVA1 and peroxisomal enzymes were included in the same cells, rats were treated daily with sub-maximal (2 or 5 mg/kg) and maximal (25 mg/kg) inducing doses of methylclofenapate for 4 days. The lobular distribution of induced proteins was determined immunocytochemically with antibodies raised against P450IVA1 and acyl-CoA oxidase. Livers from control animals showed minimal staining for both proteins. However, in the livers of animals treated with 2 or 5 mg of methylclofenapate/kg, both acyl-CoA and P450IVA immunostaining was increased, mainly in the centrilobular area. Immunostaining of serial sections revealed that these proteins were induced in the same region of the lobule. A maximal inducing dose of methylclofenapate (25 mg/kg) caused panlobular induction of both proteins. The results demonstrate that these proteins are induced in a dose-dependent manner in the same, spatially distinct, sensitive region of the liver lobule.

Endothelium in functional aortic changes of coarctation hypertension

Eleven coarctation hypertensive (CH), twelve sham control (C), and seven one-kidney, one-clip (1K,1C) rats were used to examine the role of pressure and the endothelium in vascular sensitivity changes to acetylcholine (ACh), serotonin (5-HT), and norepinephrine (NE) in chronic arterial hypertension. Terminal mean carotid artery pressures were CH = 156 +/- 5 mmHg, C = 99 +/- 3 mmHg, and 1K,1C = 159 +/- 5 mmHg. Femoral artery pressures were CH = 100 +/- 3 mmHg, C = 98 +/- 4 mmHg, and 1K,1C = 154 +/- 4 mmHg, respectively. Isometric tension recordings were made from helically cut strips of thoracic and abdominal aortas, with and without functional endothelium, from the three groups of rats. Sensitivity to relaxation by acetylcholine, expressed as -log of 50% effective dose, was significantly depressed in thoracic aortas from CH and 1K,1C rats and abdominal aortas from 1K,1C rats but not from abdominal aortas of CH rats. A similar relationship between the groups was seen for 5-HT contractions. Sensitivity to NE was enhanced in thoracic and abdominal aortas of hypertensive rats. Inactivation of aortic endothelia abolished ACh responses, did not alter 5-HT relationships between the three groups, and abolished the differences in sensitivity to NE in thoracic aortas. The data suggest that pressure and the endothelium may play a role in vascular sensitivity changes in hypertension.