FAAH deficiency promotes energy storage and enhances the motivation for food.

RATIONALE: Fatty acid amide hydrolase (FAAH) is the main degrading enzyme of the fatty acid ethanolamides anandamide (AEA) and oleoylethanolamide (OEA), which have opposite effects on food intake and energy balance. AEA, an endogenous ligand of CB(1) cannabinoid receptors, enhances food intake and energy storage, whereas OEA binds to peroxisome proliferator-activated receptors-alpha to reduce food intake and promoting lipolysis. To elucidate the role of FAAH in food intake and energy balance, we have evaluated different metabolic and behavioral responses related to feeding in FAAH-deficient (FAAH(-/-)) mice and their wild-type littermates. METHODOLOGY AND RESULTS: Total daily food intake was similar in both genotypes, but high-fat food consumption was enhanced during the dark hours and decreased during the light hours in FAAH(-/-) mice. The reinforcing and motivational effects of food were also enhanced in FAAH(-/-) mice as revealed by operant behavioral paradigms. These behavioral responses were reversed by the administration of the selective CB(1) cannabinoid antagonist rimonabant. Furthermore, body weight, total amount of adipose tissue, plasma-free fatty acids and triglyceride content in plasma, liver, skeletal muscle and adipose tissue, were increased in FAAH(-/-) mice. Accordingly, leptin levels were increased and adiponectin levels decreased in these mutants, FAAH(-/-) mice also showed enhanced plasma insulin and blood glucose levels revealing an insulin resistance. As expected, both AEA and OEA levels were increased in hypothalamus, small intestine and liver of FAAH(-/-) mice. CONCLUSION: These results indicate that the lack of FAAH predominantly promotes energy storage by food intake-independent mechanisms, through the enhancement of AEA levels rather than promoting the anorexic effects of OEA.

Upregulation of renal and vascular nitric oxide synthase in young spontaneously hypertensive rats.

The available data on the role of the L-arginine/nitric oxide (NO) pathway in the genesis of hypertension in spontaneously hypertensive rats (SHR) are limited and contradictory. In an attempt to address this issue, male SHR were studied during the early phase of evolution of hypertension (age 8 to 12 weeks) to distinguish the primary changes of NO metabolism from those caused by advanced hypertension, vasculopathy, and aging late in the course of the disease. A group of age-matched male Wistar-Kyoto rats (WKY) served as controls. The SHR exhibited a marked rise in arterial blood pressure and a significant increase in urinary excretion and plasma concentration of NO metabolites (nitrite/nitrate [NOx]). Likewise, the SHR showed a significant elevation of thoracic aorta NO synthase (NOS) activity coupled with significant increases of kidney, aorta, inducible NOS (iNOS), and endothelial NOS (eNOS) proteins. In an attempt to determine whether the enhanced L-arginine/NO pathway is a consequence of hypertension, studies were repeated using 3-week-old animals before the onset of hypertension. The study revealed significant increases in urinary NOx excretion as well as vascular eNOS and renal iNOS proteins. In conclusion, the L-arginine/NO pathway is upregulated in young SHR both before and after the onset of hypertension. Thus, development of hypertension is not due to a primary impairment of NO production in SHR. On the contrary, NO production is increased in young SHR both before and after the onset of hypertension.

Nitric oxide synthase isotype expression in salt-sensitive and salt-resistant Dahl rats.

Previous studies have suggested that salt-sensitive hypertension in humans and experimental animals may in part be due to dysregulation of the L-arginine/nitric oxide system. This study was conducted to determine the endothelial, inducible, and neuronal nitric oxide synthase expressions in the kidney, heart, aorta, and brain of salt-sensitive and salt-resistant Dahl rats. We studied salt-sensitive and salt-resistant Dahl rats maintained on high- (8%) and regular- (0.2%) salt diets for 3 weeks. Blood pressure was modestly elevated in both Dahl salt-sensitive and salt-resistant rats consuming regular diet and severely increased in sensitive but not resistant rats consuming the high-salt diet. The Dahl salt-sensitive animals showed a significant reduction in kidney, heart, and aorta inducible nitric oxide synthase protein abundance on the regular diet, with further reductions on the high-salt diet. In addition, the high-salt diet markedly downregulated endothelial nitric oxide synthase expression in the kidney and aorta but not in the heart of the Dahl salt-sensitive animals. The rise in blood pressure in the Dahl salt-sensitive rats on the high-salt diet was accompanied by a significant elevation of brain neuronal nitric oxide synthase protein. In contrast, salt-resistant animals showed no change in heart, kidney, and aorta endothelial or brain neuronal nitric oxide synthase and considerably less intense changes in inducible isotype than that seen in the salt-sensitive group in response to the high-salt diet. In conclusion, the study revealed a marked downregulation of inducible nitric oxide synthase in the Dahl salt-sensitive rats on the regular diet, with further reductions on the high-salt diet. Furthermore, Dahl salt-sensitive rats consuming the high-salt diet showed significant reductions of kidney and aorta endothelial nitric oxide synthase and an upregulation of brain neuronal nitric oxide synthase expression.

Induction of oxidative stress by glutathione depletion causes severe hypertension in normal rats.

Several recent studies have shown that certain forms of genetic or acquired hypertension are associated with oxidative stress and that animals with those types of hypertension respond favorably to antioxidant therapy. We hypothesize that oxidative stress may cause hypertension via (among other mechanisms) enhanced oxidation and inactivation of nitric oxide (NO). To test this hypothesis, Sprague-Dawley rats were subjected to oxidative stress by glutathione (GSH) depletion by means of the GSH synthase inhibitor buthionine sulfoximine (BSO, 30 mmol/L in drinking water) for 2 weeks. The control group was given drug-free drinking water. In parallel experiments, subgroups of animals were provided vitamin E-fortified chow and vitamin C-supplemented drinking water. The BSO-treated group showed a 3-fold decrease in tissue GSH content, a marked elevation in blood pressure, and a significant reduction in the urinary excretion of the NO metabolite nitrate plus nitrite, which suggests depressed NO availability. These characteristics were associated with a significant accumulation in various tissues of nitrotyrosine, which is the footprint of NO inactivation by reactive oxygen species. Administration of vitamin E plus vitamin C ameliorated hypertension, improved urinary nitrate-plus-nitrite excretion, and mitigated nitrotyrosine accumulation (despite GSH depletion) in the BSO-treated animals but had no effect in the control group. In conclusion, GSH depletion resulted in perturbation of the NO system and severe hypertension in normal animals. The effects of BSO were mitigated by concomitant antioxidant therapy despite GSH depletion, which supports the notion that oxidative stress was involved in the pathogenesis of hypertension in this model.

Lead-induced hypertension is not associated with altered vascular reactivity in vitro.

In confirmation of a previous study (Am J Hypertens 1993;6:723), mean arterial blood pressure (MBP), as determined by tail cuff plethysmography, was found to be significantly elevated in Sprague-Dawley rats after 3 months of feeding 0.48 mmol/L (100 ppm) lead acetate/day (144 +/- 3.3 [SEM], in lead-treated [L] v 107 +/- 3.3 mm Hg in controls [C], P < .001). Thoracic aorta was excised from L and C animals (n = 6). Segments were suspended in tissue baths with Krebs' bicarbonate solution, then tested sequentially for vasoreactivity to 68 mmol/L K+, followed by graded concentrations of phenylephrine (PE), 0.01 to 0.3 micromol/L, acetylcholine (Ach), 0.001 to 3 micromol/L, nitroprusside (SNP), 0.0001 to 0.1 micromol/L, norepinephrine (NE), 0.001 to 300 micromol/L. There were no differences between L and C animals with respect to either vasoconstrictors (PE and NE) or vasodilators (Ach and SNP). The tissue levels of cGMP measured with and without phosphodiesterase inhibition, and in the absence and presence of either Ach or SNP, were comparable in the two groups. We conclude that the intrinsic vascular responsiveness is unchanged in lead-treated animals. The elevation of MBP is due to the presence of circulating factor(s) and hemodynamic changes.

Radiodetoxified endotoxin-induced tolerance alters monocyte but not neutrophil CD11b and CD18 expression in response to lipopolysaccharide.

OBJECTIVES: To test the hypothesis that pretreatment with radiodetoxified endotoxin (RDE) may mitigate the deleterious effects of subsequent infection, in part by modifying leukocyte adhesion receptor expression, and to investigate the cellular mechanisms of endotoxin tolerance induced by RDE. DESIGN: To assess the effect of RDE pretreatment on mortality from bacterial peritonitis, rats were implanted with an intraperitoneal, barium-fecal inoculum at intervals of 0, 1, 3, and 5 days after RDE injection. Experiments were then conducted to test the effect on leukocyte adhesion receptor expression. Two groups of mice received saline solution, and one group, RDE. After 72 hours, one group received saline solution (saline/saline group), the others, lipopolysaccharide (LPS) (saline/LPS and RDE/LPS groups). Peripheral leukocytes were obtained 1 hour after injection and were analyzed for CD11b and CD18 expression by flow cytometry. SETTING: Laboratory animal study. RESULTS: Survival rates were not improved in rats that were pretreated with RDE 0 and 24 hours before inoculum (0% and 7%, respectively). In rats that were pretreated 72 hours and 120 hours before inoculum, 47% (P < .01) and 60% (P < .01) survived, respectively. CD18 expression on polymorphonuclear leukocytes increased twofold in the RDE/LPS (mean +/- SEM, 300.3 +/- 32.9) and the saline/LPS (mean +/- SEM, 360.4 +/- 59.9) groups compared with controls (mean +/- SEM, 176.4 +/- 18.9) (P < .05). CD11b expression on polymorphonuclear leukocytes increased threefold in the RDE/LPS (mean +/- SEM, 91.3 +/- 8.1) and the saline/LPS (mean +/- SEM, 89.8 +/- 11.4) groups compared with controls (mean +/- SEM, 32.1 +/- 1.8) (P < .05). CD18 expression on monocytes decreased in the saline/LPS group (mean +/- SEM, 134.2 +/- 14.2) and was unchanged in the RDE/LPS group (mean +/- SEM, 200.2 +/- 17.2) compared with controls (mean +/- SEM, 217.6 +/- 16.5) (P < .05). CD11b expression on monocytes decreased in the saline/LPS group (mean +/- SEM, 25.8 +/- 2.2) and was unchanged in the RDE/LPS group (mean +/- SEM, 36.4 +/- 0.9) compared with controls (mean +/- SEM, 39.7 +/- 3.9) (P < .05). CONCLUSIONS: Radiodetoxified endotoxin reduces mortality rates from bacterial peritonitis when given at least 72 hours prior to a bacterial inoculum. Tolerance to subsequent LPS challenge is associated with an abrogation of the reduced peripheral monocyte CD11b and CD18 expression observed in native LPS-stimulated mice but is not associated with changes in polymorphonuclear leukocyte CD11b and CD18 expression. The mechanism of the observed RDE-induced monocyte hyporesponsiveness to LPS and its possible protective effect is uncertain and requires further investigation.

The effect of pregnancy on renal clearance of boron in rats given boric acid orally.

Boric acid (H(3)BO(3)) has been shown to cause developmental abnormalities in the offspring of pregnant rats. Comparative data on the renal clearance of boron (B) in rats and humans, both pregnant and nonpregnant, exposed to boric acid (BA) would reduce uncertainty in interspecies extrapolation from rats to humans. The purpose of this study was to evaluate the effect of pregnancy on the plasma half-life and renal clearance of boron in Sprague-Dawley rats given a single oral dose of boric acid. For the half-life study, nonpregnant and pregnant (gestation day 16) rats were given a single dose of 30 mg/kg of boric acid by gavage, and plasma samples were collected at 2-3 h intervals. The plasma half-life of boron was determined to be 2.9 +/- 0.2 and 3.2 +/- 0.3 h in nonpregnant and pregnant rats, respectively. In the clearance study, nonpregnant and pregnant (GD 16) rats were given a single gavage dose of 0.3, 3, or 30 mg/kg of boric acid. Boron clearance was slightly higher in pregnant rats (3.3 +/- 0.6, 3.2 +/- 0.5, and 3.4 +/- 0.5 ml/min/kg, respectively) compared to nonpregnant rats (3.1 +/- 0.8, 3.0 +/- 0.6, and 3.2 +/- 0.5 ml/min/kg, respectively), but the difference was not statistically significant and not dose-related. Boron clearance was less than creatinine clearance, suggesting tubular reabsorption in both groups. In conclusion, pregnancy did not appear to significantly alter the renal clearance or the plasma half-life of boron in Sprague-Dawley rats under the conditions of this study.

Intestinal absorption of arachidonic acid in experimental azotemia.

The effect of renal failure (RF) on intestinal absorption of dietary fatty acids is not known. We studied the intestinal absorption of arachidonic acid (AA) in rats with experimental short-term (2 weeks post-subtotal nephrectomy) and long-term (5-6 weeks post-subtotal nephrectomy) RF. The results were compared with those obtained in sham-operated animals on liberal food intake (NL) and in those pair-fed (PF) with the respective RF groups. In vivo perfusion and in vitro incubation experiments were performed at a wide range of AA concentrations. The rates of AA transport determined both in vivo and in vitro were significantly lower in the short-term RF group than those found in the NL controls and the PF animals who showed comparable values. In contrast animals with long-term RF exhibited an increased rate of AA transport as compared with the respective controls. The observed changes in the transport rates appeared to parallel directional changes in mucosal mass which was reduced in animals with short-term RF and restored in those with long-term RF.

Social isolation and chronic handling alter endocannabinoid signaling and behavioral reactivity to context in adult rats.

Social deprivation in early life disrupts emotionality and attentional processes in humans. Rearing rats in isolation reproduces some of these abnormalities, which are attenuated by daily handling. However, the neurochemical mechanisms underlying these responses remain poorly understood. We hypothesized that post-weaning social isolation alters the endocannabinoid system, a neuromodulatory system that controls emotional responding. We characterized behavioral consequences of social isolation and evaluated whether handling would reverse social isolation-induced alterations in behavioral reactivity to context and the endocannabinoid system. At weaning, pups were single or group housed and concomitantly handled or not handled daily until adulthood. Rats were tested in emotionality- and attentional-sensitive behavioral assays (open field, elevated plus maze, startle and prepulse inhibition). Cannabinoid receptor densities and endocannabinoid levels were quantified in a separate group of rats. Social isolation negatively altered behavioral responding. Socially-isolated rats that were handled showed less deficits in the open field, elevated plus maze, and prepulse inhibition tests. Social isolation produced site-specific alterations (supraoptic nucleus, ventrolateral thalamus, rostral striatum) in cannabinoid receptor densities compared to group rearing. Handling altered the endocannabinoid system in neural circuitry controlling emotional expression. Handling altered endocannabinoid content (prefrontal and piriform cortices, nucleus accumbens) and cannabinoid receptor densities (lateral globus pallidus, cingulate and piriform cortices, hippocampus) in a region-specific manner. Some effects of social isolation on the endocannabinoid system were moderated by handling. Isolates were unresponsive to handling-induced increases in cannabinoid receptor densities (caudal striatum, anterior thalamus), but were sensitive to handling-induced changes in endocannabinoid content (piriform, prefrontal cortices), compared to group-reared rats. Our findings suggest alterations in the endocannabinoid system may contribute to the abnormal isolate phenotype. Handling modifies the endocannabinoid system and behavioral reactivity to context, but surmounts only some effects of social isolation. These data implicate a pivotal role for the endocannabinoid system in stress adaptation and emotionality-related disturbances.

Regulation of food intake by oleoylethanolamide.

Oleoylethanolamide (OEA), the naturally occurring amide of ethanolamine and oleic acid, is an endogenous lipid that modulates feeding, body weight and lipid metabolism by binding with high affinity to the ligand-activated transcription factor, peroxisome proliferator-activated receptor-alpha (PPAR-alpha). In the present article, we describe the biochemical pathways responsible for the initiation and termination of OEA signaling, and outline the pharmacological properties of this compound in relation to its ability to activate PPAR-alpha. Finally, we discuss the possible role of OEA as a peripheral satiety hormone.

Role of secondary hyperparathyroidism in the genesis of hypertriglyceridemia and VLDL receptor deficiency in chronic renal failure.

Recent studies have revealed marked down-regulation of hepatic lipase (HL), lipoprotein lipase (LPL) and very low density lipoprotein-receptor (VLDL-R) expressions in animals with chronic renal failure (CRF). Acquired deficiency of these proteins, which together play an important role in catabolism of triglyceride-rich lipoproteins, is involved in the pathogenesis of CRF hypertriglyceridemia. Down-regulation of HL and LPL expressions in CRF can be completely reversed by parathyroidectomy (PTx), suggesting the role of excess parathormone (PTH). However, the role of hyperparathyroidism in the pathogenesis of CRF-induced VLDL-R deficiency has not been investigated before, and was studied here. To this end, VLDL-R mRNA (Northern analysis) and VLDL-R protein (Western analysis) of the fat pad and soleus muscle were compared in CRF (5/6 nephrectomized) rats, CRF animals with PTx (CRF-PTx) and sham-operated control animals. The CRF animals exhibited marked hypertriglyceridemia coupled with significant reductions in skeletal muscle and adipose tissue VLDL-R mRNA abundance and protein mass. Parathyroidectomy resulted in a significant, but partial, amelioration of CRF hypertriglyceridemia. However, in contrast to its effect on HL and LPL expressions, PTx did not improve VLDL-R expression, suggesting a PTH-independent mechanism for the latter abnormality. The differential effect of PTx on HL and LPL on the one hand and VLDL-R on the other can, in part, account for partial as opposed to complete correction of the associated hypertriglyceridemia with PTx in the CRF animals.

Role of increased oxygen free radical activity in the pathogenesis of uremic hypertension.

Earlier studies have demonstrated increased oxygen free radical (OFR) activity, diminished antioxidant capacity and reduced OFR-inactivating enzymes in chronic renal failure (CRF). Via inactivation of nitric oxide (NO), oxidation of arachidonic acid and a direct vasoconstrictive action, OFR can potentially raise blood pressure (BP). This study was designed to test the hypothesis that increased OFR activity may contribute to CRF hypertension. Four weeks after 5/6 nephrectomy rats were treated for two weeks with either lazaroid, a potent antioxidant and lipid peroxidation inhibitor (CRF-LZ group), or vehicle alone (CRF group) by daily gastric gavage. The control group was sham operated and placebo treated. The CRF group exhibited significant increases in BP and plasma lipid peroxidation product, malondialdehyde (MDA), indicating enhanced OFR activity. This was accompanied by decreased urinary nitrate/nitrite (NOx) excretion suggesting depressed NO production. LZ therapy normalized plasma MDA and significantly ameliorated CRF-induced hypertension. Both MDA and blood pressure (BP) rose to values seen in the untreated CRF group within two weeks after termination of LZ therapy. Intravenous administration of the hydroxyl radical scavenger, dimethylthiourea (DMTU), significantly lowered BP and raised urinary NOx excretion. However, no discernible effects were found with either superoxide dismutase or catalase (superoxide and H2O2 quenchers). The results suggest that increased OFR activity is, in part, responsible for CRF-associated HTN. The study further points to hydroxyl radicals as the major source of OFR in CRF animals. If substantiated in humans, antioxidant therapy becomes a logical adjunct in the management of CRF.

Gene expression of hepatic cholesterol 7 alpha-hydroxylase in the course of puromycin-induced nephrosis.

Cholesterol conversion to and biliary excretion of bile acids represents the principal pathway of cholesterol catabolism in mammals. Cholesterol 7 alpha-hydroxylase (Ch-7 alpha-H) is the first and the rate limiting step in bile acid production. Recently, Ch-7 alpha-H enzymatic activity has been shown to be normal in rats with established puromycin aminonucleoside-induced nephrosis (NS). To our knowledge, the gene expression of Ch-7 alpha-H in NS has not been investigated. We measured hepatic Ch-7 alpha-H mRNA and protein (by Northern and Western blot analyses) in rats at baseline and longitudinally during the course of induction and chronic phase of puromycin (PAN) induced NS. Groups of placebo-treated (controls) and diet-induced hypercholesterolemic (DHC) rats were included for comparison. The NS and DHC animals exhibited severe hypercholesterolemia of similar magnitude. Hepatic Ch-7 alpha-H transcript and protein remained virtually unchanged throughout the study period in the NS group. In contrast, Ch-7 alpha-H gene expression was markedly up-regulated in the DHC group. These observations suggest that hepatic Ch-7 alpha-H gene expression may be inappropriately low for the degree of the associated hypercholesterolemia in the NS group. It should be noted, however, that hepatic tissue cholesterol concentration was normal in the NS group and greatly increased in the DHC group. This can account for the disparity in Ch-7 alpha-H mRNA levels between the two groups since intracellular rather than extracellular cholesterol modulates Ch-7 alpha-H gene expression. In conclusion, the present study revealed that hepatic Ch-7 alpha-H gene expression remains unchanged during the course of PAN-induced NS in rats. It thus appears that generation and maintenance of hypercholesterolemia in this model of NS does not involve significant alteration of Ch-7 alpha-H gene expression.

Effect of chronic renal failure on intestinal transport of biotin in the rat.

The present study examined the effect of chronic renal failure (RF) on biotin transport in rat intestine. Chronic RF was induced by subjecting rats to right nephrectomy and left two-thirds nephrectomy. Control rats underwent sham operation but without tissue removal and were pair fed. Transport studies were performed 5 to 6 weeks after operation. Chronic RF was found to cause a marked decrease in the maximal velocity (Vmax) of biotin mucosal-to-serosal transport in jejunal everted sacs with minimal change in the apparent Michaelis-Menten constant (Km) of the transport process. This impairment in biotin transport was found to involve the transport process of the vitamin across the brush border membrane (BBM) domain of the enterocyte as shown by studies with BBM vesicles (BBMVs). These studies with BBMV similarly showed a decrease in the Vmax of biotin transport with minimal change in the apparent Km. The impairment of biotin transport in intestinal BBMVs was not due to dissipation of the Na+ gradient across the BBM (which is the driving force of biotin movement across this membrane) because transport of sodium 22 was found to be similar in BBMVs prepared from the RF rats and the sham-operated PF control rats. These results demonstrate that chronic RF in rats causes impairment in biotin intestinal transport. This impairment is due to a decrease in the number (and/or activity) of the biotin transport carriers and involves the transport process of biotin at the BBM.

Effect of antioxidant therapy on blood pressure and NO synthase expression in hypertensive rats.

Earlier studies have demonstrated evidence for increased reactive oxygen species, enhanced NO synthase (NOS) expression, and elevated NO production in spontaneously hypertensive rats (SHR). Given the negative-feedback regulation of NOS by NO, we hypothesized that enhanced NO inactivation by ROS may contribute to compensatory upregulation of NOS in SHR. The present study was designed to test this hypothesis. Eight-week-old male SHR and Wistar-Kyoto rats were treated for 3 weeks with either a placebo or the potent antioxidant, lazaroid (desmethyltirilazad, 10 mg. kg(-1). d(-1), by gastric gavage). Tail arterial blood pressure, urinary excretion of NO metabolites (ie, nitrate and nitrite), and immunodetectable NOS isotype proteins in the vascular, renal, cardiac, and cerebral tissues were measured. The placebo-treated SHR group showed a marked elevation of blood pressure and a significant upregulation of aorta, kidney, and cardiac tissue endothelial and inducible NOS (eNOS and iNOS, respectively) proteins and of brain and renal tissue neuronal NOS. Lazaroid therapy ameliorated hypertension and mitigated the upregulation of eNOS and iNOS in vascular, renal, and cardiac tissues but had limited effect on the expression of renal and brain neuronal NOS. In contrast, lazaroid therapy had no effect on blood pressure, urinary nitrate and nitrite excretion, or tissue NOS isotype expressions in the Wistar-Kyoto group. These findings support the role of oxidative stress in the genesis and/or maintenance of hypertension and compensatory upregulation of the expression of eNOS and iNOS in SHR.

Vitamin D absorption, plasma concentration and urinary excretion of 25-hydroxyvitamin D in nephrotic syndrome.

Nephrotic syndrome (NS) is commonly associated with vitamin D deficiency. Urinary losses of the protein-bound intermediary metabolite of this vitamin is thought to contribute to the deficiency state. The role of possible changes, if any, of vitamin D absorption has not been investigated previously in NS. We determined intestinal absorption of vitamin D3 as well as plasma concentration and urinary excretion of 25-hydroxyvitamin D3 in rats with puromycin aminonucleoside-induced NS. In vivo recirculating perfusion technique was employed at 100 and 600 nM perfusate concentrations. The results were compared with those obtained in animals receiving placebo injections provided with either free access to food (normal controls) or those pair-fed with their NS counterparts (pair-fed group). The NS group showed heavy proteinuria and hypoalbuminemia. In addition, the NS group exhibited marked urinary losses and significantly reduced plasma concentration of 25-hydroxyvitamin D. The rate of vitamin D3 absorption (given as nmol/100 cm/min) at 100 nM perfusate concentration in the NS group (0.161 +/- 0.029) was not significantly different from those obtained in the pair-fed group (0.202 +/- 0.058) and the normal control group (0.143 +/- 0.053). Likewise, no significant difference was found in the rats of vitamin D absorption at 600 nM concentration among the NS (1.073 +/- 0.383), pair-fed (0.955 +/- 0.229), and normal control (0.756 +/- 0.314) groups. Accordingly, intestinal absorption of vitamin D appears to be unaffected by the presence of experimental NS and as such the associated vitamin D deficiency can be managed by enteral supplementation.

Antithrombin III inhibits mesangial cell proliferation.

Thrombin stimulates and heparin and heparan sulfate inhibit mesangial cell proliferation. In addition, heparin has been shown to inhibit thrombin-stimulated smooth muscle cell proliferation. The anticoagulant action of heparin is mediated by antithrombin III. This study investigated whether heparin's antiproliferative action is also mediated by antithrombin III. To this end, the effect of antithrombin III on thrombin-stimulated mesangial cell growth was examined. As expected, thrombin stimulated DNA synthesis and cell growth in cultured human mesangial cells. The effect of thrombin on DNA synthesis and mesangial cell proliferation was inhibited by standard heparin and antithrombin III, separately or together. The magnitude of the inhibitory action of antithrombin III was equal to that of equimolar concentrations of heparin and that observed with the combination of the two. Experiments carried out in serum (hence antithrombin III)-free medium revealed that heparin's inhibitory effects are independent of antithrombin III. It was concluded that antithrombin III, an endogenous inhibitor of thrombin's coagulant activity, is an equally effective inhibitor of thrombin's mitogenic action.

Intestinal absorption of L-ascorbic acid in rats with renal failure.

We studied L-ascorbic acid absorption in rats subjected to subtotal nephrectomy (renal failure (RF) group) and compared the results with those obtained in sham-operated normal animals and those pair-fed with their azotemic counterparts (PF group). In vivo recirculating perfusion and in vitro everted sac techniques were employed. The in vitro experiments were repeated substituting buffer within the serosal compartment with pooled sera from uremic and normal individuals. L-Ascorbic acid absorption in vivo in the RF group was significantly lower than those found in normal control and PF groups. In contrast, the in vitro mucosal to serosal transport was increased in the RF and PF groups when compared with the normal control group, suggesting increased permeability to L-ascorbic acid in the former groups. The disparity between in vivo and in vitro results in the RF animals is indicative of some inhibitory influence present in the intact uremic animals. However, experiments comparing the effect of uremic with normal sera on in vitro transport failed to reveal any suppressive effect of uremic chemical environment. In addition, serum ascorbic acid was reduced in PF and RF groups when compared with the normal control animals, thereby excluding elevated blood level as a cause of impaired absorption in intact animals with RF. In conclusion, in vivo jejunal absorption of L-ascorbic acid is impaired in rats with RF despite evidence of increased in vitro permeability. The latter appears to be mediated by reduced nutrient intake and weight loss. The inhibitory influence present in vivo could not be reproduced by incubation with uremic sera in vitro.

Intestinal absorption of vitamin E in experimental renal failure.

We studied intestinal absorption of vitamin E in rats with experimental renal failure (RF) and in sham-operated normal and pair-fed controls using in vivo perfusion and in vitro everted sacs. The in vivo absorption rates per unit of intestine length were significantly reduced in RF and pair-fed groups. Expression of data per unit of intestine weight gave normal values in the pair-fed but depressed values in the RF animals. Vitamin E uptake in vitro was significantly increased in RF animals, suggesting enhanced permeability. We conclude: (i) vitamin E absorption in vivo is impaired in experimental RF; (ii) this is in part due to reduced nutrient intake; and (iii) disparity between in vivo and in vitro results suggests the presence of some inhibitory influence(s) in intact animals with RF.

The pituitary-gonadal axis in experimental nephrotic syndrome in male rats.

Basal and luteinizing releasing hormone-stimulated gonadotropin secretion were studied in male rats made nephrotic with puromycin, and in pair-fed and normal control animals. In addition, plasma concentrations of testosterone, androstenedione, estradiol, and estrone were measured in the three groups of animals. Urinary testosterone concentrations were also measured in the three experimental groups. The data showed that basal luteinizing hormone concentration was significantly elevated in the nephrotic group compared with the pair-fed and normal control groups. Gonadotropin response to luteinizing releasing hormone stimulation was not significantly different in the three groups, suggesting an intact hypothalamic-pituitary axis in nephrotic syndrome. Urinary testosterone concentration in the nephrotic animals was significantly higher than in the pair-fed and normal control groups. Plasma testosterone, androstenedione, estradiol, and estrone concentrations were significantly lower in the nephrotic and pair-fed animals than in the normal control animals, indicating possibly impaired gonadal steroidogenesis in these two groups that may be related to the catabolic state of the animals. It thus appears that urinary loss of protein-bound (sex hormone binding globulin-bound) testosterone in the nephrotic syndrome leads to increased basal secretion of luteinizing hormone, presumably as a result of increased luteinizing releasing hormone secretion. This occurs to compensate for the abnormal urinary testosterone loss and is an attempt to restore plasma testosterone concentrations to normal. The higher basal plasma luteinizing hormone concentration in the nephrotic group supports this conclusion.(ABSTRACT TRUNCATED AT 250 WORDS)