Acute and chronic effects of ethanol on secretion of alpha-tocopherol from primary cultures of rat hepatocytes

Primary cultures of rat hepatocytes were used to study the effect of acute and chronic ethanol exposure on alpha-tocopherol content in cells and media. Cells treated acutely with 60 mM ethanol secreted 74.5 +/- 18.0% (P less than 0.05), and their cellular alpha-tocopherol content was 85.7 +/- 15.4% (not significant) of controls after 20 h incubation. At this time total recovery of alpha-tocopherol was significantly reduced in ethanol-exposed cells (43.1 +/- 8.4%) as compared to control cells (52.8 +/- 5.0%, P less than 0.05). Hepatocytes isolated from chronic ethanol-fed rats (35% of total energy intake as ethanol for 5 weeks) secreted 41.9 +/- 12.7% less alpha-tocopherol than did cells of pair-fed controls during 20 h incubation (P less than 0.05). The amount of alpha-tocopherol secreted was then 15.6 +/- 4.2 and 19.8 +/- 3.8% of cell-associated alpha-tocopherol at start of incubation for chronic ethanol-fed and control rats, respectively (P less than 0.05). When 60 mM ethanol was added to the incubation medium, hepatocytes of control rats secreted significantly less alpha-tocopherol (about 30%, P less than 0.05), whereas alpha-tocopherol secretion was not significantly reduced in hepatocytes of chronic ethanol-fed rats. We conclude that both acute and chronic ethanol exposure reduce alpha-tocopherol secretion from rat hepatocytes.     

Effect of inhalation of insecticide spray on learning and memory in rats

Acute exposure to insecticide (Baygon-spray; 5 ml/animal/5 min) inhalation in rats did not affect the learning process but produced a significant loss of memory (P less than 0.01 less than 0.001) whereas chronic exposure (one exposure per day for three weeks) produced a significant delay in learning (P less than 0.05) and memory (P less than 0.01). Acetylcholinesterase activity in brain after acute and chronic exposure declined significantly (P less than 0.01) during the learning process but returned to normal after 24 hr.     

Bidirectional Alterations of GABAA Receptor Subunit Peptide Levels in Rat Cortex During Chronic Ethanol Consumption and Withdrawal

Abstract: The pharmacological properties of γ-aminobutyric acid_A (GABA_A) receptors are altered by prolonged exposure to ethanol both in vivo and in vitro. We have shown previously that prolonged ethanol exposure elicits selective alterations in various GABA_A receptor subunit mRNA levels in rat cerebral cortex. Some of these effects are rapidly reversed during ethanol withdrawal. The present study was conducted to determine the effects of prolonged ethanol exposure (dependence) and ethanol withdrawal on cerebral cortical peptide expression for several subunits. GABA_A receptor α1 subunit peptide levels were decreased by nearly 40%, whereas α4 subunit peptide levels were increased by 27% in both ethanol-dependent and withdrawn rats. These changes correlate well with observed alterations in mRNA levels following prolonged ethanol exposure in dependent rats, but do not match the effects on mRNA levels during ethanol withdrawal. β2/3 subunit peptide levels increased by ～32% in both ethanol-dependent rats and rats undergoing ethanol withdrawal. We observed a 30–60% increase in γ1 subunit peptide levels in both dependent rats and those undergoing withdrawal, also correlating with the previous report on ethanol-induced alterations in mRNA levels. Peptide levels for γ2 subunits did not differ from control values in either condition. These findings show that specific alterations in GABA_A receptor subunit peptide levels are associated with ethanol dependence in rats. GABA_A receptor subunit peptide expression is more stable than mRNA expression, and mRNA levels are not representative of peptide expression during ethanol withdrawal. These findings are consistent with the suggestion that alterations in GABA_A receptor gene expression underlie the functional properties of GABA_A receptors in ethanol-dependent rats and those undergoing ethanol withdrawal.     

Responses of the rat pituitary-adrenal axis to hypotensive infusions of corticotropin-releasing factor, vasoactive intestinal peptide and other depressor agents.

We have assessed in male rats the response of the hypothalamo-pituitary-adrenal axis to hypotension induced by 30 min i.v. infusions of corticotropin-releasing factor (CRF; 0.1, 0.2 and 0.5 nmol/kg/min), calcitonin gene-related peptide (CGRP; 0.25 nmol/kg/min), vasoactive intestinal peptide (VIP; 0.25 nmol/kg/min) and nitroprusside (NP; 150 micrograms/kg/min). Infusions of CRF produced dose-dependent decreases in mean arterial blood pressure of 10, 35 and 43 mmHg at 30 min, and the other treatment had depressor effects comparable with the higher CRF doses (between -35 and -44 mmHg). Plasma ACTH levels were increased from 383% to 595% by CGRP, NP and the three different CRF infusions (P less than 0.001 vs. controls), whereas they were raised more than 10-fold by VIP administration (P less than 0.001 vs. other treatments), a level 60% higher than the maximum achieved with CRF. Corticosterone levels were increased by 112% to 146% following infusion of the three different CRF doses, CGRP and NP (P less than 0.001 vs. controls), and by 240% after VIP (P less than 0.001 vs. other treatments). Plasma aldosterone values were increased by 112% to 140% after infusion of NP and the two higher CRF doses (P less than 0.01 vs. controls), and by 223% following VIP (P less than 0.05 vs. CRF 0.2 and NP). CGRP infusion, although resulting in similar haemodynamic changes, did not alter circulating aldosterone. The levels measured after CGRP were identical to those observed after the infusion of atrial natriuretic peptide (ANP; 1 nmol/kg/min), a known inhibitor of aldosterone secretion. These results demonstrate that the combination of hypotension and direct pituitary stimulation by CRF does not increase circulating ACTH levels above those obtained with hypotension alone (NP and CGRP), whereas VIP, which has only minimal direct effects on corticotroph function, markedly enhanced the ACTH response, suggesting that it may modulate ACTH release by an indirect mechanism. Evaluation of aldosterone levels after the different infusions indicates that CGRP prevented the rise normally associated with acute hypotension, thus confirming recent observations in other species that stimulated aldosterone secretion can be inhibited by CGRP.     

Ovariectomy has minimal effects on neuroadaptations associated with ethanol dependence in female rats

We previously found gender selective alterations in gene expression for GABA_A and NMDA receptors associated with the development of ethanol dependence. Males and females have a differing hormonal environment, including steroid hormone derivatives (neuroactive steroids) that exert effects at GABA_A and NMDA receptors. Therefore, we explored whether the removal of ovarian steroids would alter gender differences in response to chronic ethanol exposure. We found that ovariectomy reduced ethanol drinking levels by 15%, comparable to earlier observations between intact female and male rats. However, investigation of the effects of chronic ethanol exposure on intact versus ovariectomized female rats uncovered few differences in chronic ethanol-induced alterations in selected GABA_A or NMDA receptor subunit peptide levels. In general, findings for both groups of females were similar to previous observations. There was no reduction in GABA_A receptor 1 subunit levels in cerebral cortex in either intact or ovariectomized female rats, in contrast to the significant reduction observed in male rats. In addition, both intact and ovariectomized female rats had increased levels of the NMDA NR1 subunit in cerebral cortex and hypothalamus, but not in hippocampus, whereas ethanol dependent male rats displayed significant increases in the NR1 subunit only in hippocampus. Radioligand binding analysis with [³⁵S]TBPS found no differences in modulation of the GABA_A receptor by neuroactive steroids between ethanol dependent male, intact female or ovariectomized female rats. Seizure susceptibility was not different between intact or ovariectomized female rats during ethanol withdrawal. We did observe differential effects on brain allopregnanolone and plasma corticosterone levels between ethanol dependent intact and ovariectomized female rats, suggesting that ovarian steroids influence HPA axis adaptations to prolonged ethanol exposure. Overall, these data suggest that ovarian steroids do not significantly impact the gender selective alterations of GABA_A and NMDA receptors associated with ethanol dependence.     

Distribution of 3H-proline within transseptal fibers of the rat following release of orthodontic forces

Maxillary right first molar teeth of rats were tipped mesially with an orthodontic appliance for 2 weeks (experimental group), 3H-proline was injected, and orthodontic forces were removed 6 hr later (time 0). The contralateral molar teeth of treated (internal control group) and age- and weight-matched untreated animals (external control group) were also studied. Diastemata were created between the molar teeth by the orthodontic appliance, and transseptal fibers between first and second (P less than 0.001) and second and third molars (P less than 0.005) were significantly lengthened as compared to external and internal controls at time 0. Diastemata between molar teeth were closed 5 days after removal of orthodontic force. Transseptal fibers adjacent to the source of the orthodontic force (mesial region) had the highest mean number of 3H-proline-labeled proteins at time 0 and at all times following removal of the force (P less than 0.001), and had the highest rate of labeled protein removal (P less than 0.001). Half-lives for removal of 3H-proline-labeled transseptal fiber proteins were significantly greater in mesial and distal regions and significantly less in middle regions of experimentals than in corresponding regions of external controls (P less than 0.001). These data suggest the following: 1) transseptal fibers adjust their length by rapid remodeling in regions experiencing a tensile force; 2) collagenous protein turnover within the middle third of the transseptal fibers is more rapid subsequent to release of orthodontic force than during normal physiologic drift, suggesting that this region adapts rapidly to changes in adjacent tooth position and that these fibers do not play a significant role in relapse of orthodontically relocated teeth; and 3) significant differences in turnover rates of 3H-proline-labeled transseptal ligament proteins of external and internal control quadrants suggest that tooth movement produces both local and systemic effects on collagenous protein metabolism.     

The lack of CB1 receptors prevents neuroadapatations of both NMDA and GABA(A) receptors after chronic ethanol exposure

As the contribution of cannabinoid (CB1) receptors in the neuroadaptations following chronic alcohol exposure is unknown, we investigated the neuroadaptations induced by chronic alcohol exposure on both NMDA and GABA(A) receptors in CB1-/- mice. Our results show that basal levels of hippocampal [(3)H]MK-801 ((1)-5-methyl-10,11-dihydro-5Hdibenzo[a,d]cyclohepten-5,10-imine) binding sites were decreased in CB1-/- mice and that these mice were also less sensitive to the locomotor effects of MK-801. Basal level of both hippocampal and cerebellar [(3)H]muscimol binding was lower and sensitivity to the hypothermic effects of diazepam and pentobarbital was increased in CB1-/- mice. GABA(A)alpha1, beta2, and gamma2 and NMDA receptor (NR) 1 and 2B subunit mRNA levels were altered in striatum of CB1-/- mice. Our results also showed that [(3)H]MK-801 binding sites were increased in cerebral cortex and hippocampus after chronic ethanol ingestion only in wild-type mice. Chronic ethanol ingestion did not modify the sensitivity to the locomotor effects of MK-801 in both genotypes. Similarly, chronic ethanol ingestion reduced the number of [(3)H]muscimol binding sites in cerebral cortex, but not in cerebellum, only in CB1+/+ mice. We conclude that lifelong deletion of CB1 receptors impairs neuroadaptations of both NMDA and GABA(A) receptors after chronic ethanol exposure and that the endocannabinoid/CB1 receptor system is involved in alcohol dependence.     

Feeding rats a diet enriched with saturated fatty acids prevents the inhibitory effects of acute and chronic ethanol exposure on the in vitro uptake of hexoses and lipids

Chow-fed rats were given 15% ethanol in their drinking water for 4 weeks, and then for the next 2 weeks of ethanol exposure they were fed isocaloric semisynthetic diets enriched in either saturated (S) or polyunsaturated (P, linoleic acid) fats. Food intake was lower in ethanol-fed (ETH) than in control (C) rats, but the average body weight gain was similar in ETH and C fed S or P. Intestinal dry weight and the percentage of the intestinal wall comprised of mucosa were more than 2-fold higher in ETH than C fed P, whereas these values were 50% lower in ETH than C fed S. The in vitro jejunal uptake of glucose and galactose was higher in ETH than C fed S, whereas the converse was true when feeding P. These effects were due to differences in the values of the maximal transport rate (Vmax), the Michaelis constant (Km), and the contribution of passive permeation. The relative permeability of the intestine to lipids was unchanged by giving ethanol or by feeding S or P, but the individual rates of uptake of most medium- and long-chain fatty acids and cholesterol were lower in ETH fed P as compared with S. In a second series of studies the acute effect of ethanol exposure was examined: animals were fed S or P for 2 weeks and the intestine was then removed: when 5% ethanol was added directly to the test solutions, there was lower in vitro jejunal and ileal uptake of glucose and higher jejunal uptake of 18:2 when rats were previously fed P, but not in those fed S. In summary; (1) feeding an isocaloric polyunsaturated fatty acid diet has a trophic effect on the intestinal mucosa of animals chronically drinking ethanol; and (2) feeding rats a diet enriched with saturated fatty acids prevents the inhibitory effects of acute and chronic ethanol exposure on the in vitro jejunal uptake of glucose, galactose and lipids observed in animals fed a polyunsaturated diet. Thus, the effect of chronic consumption of ethanol on the active and passive jejunal uptake of nutrients is influenced by the type of lipids in the animal's diet.     

Ethanol intoxication increases hepatic N-lysyl protein acetylation

The acetylation of the ε-amino group of lysine to form N-acetyl lysine (N-AcLys)-modified proteins regulates the activity of metabolic proteins. Because of the multiple effects of ethanol upon hepatic metabolism, it was hypothesized that ethanol exposure increases the hepatic content of N-AcLys-modified proteins. To test this hypothesis, rats or mice were exposed to ethanol using a liquid diet regimen. Content of N-AcLys-modified proteins was elevated more than 5-fold after 6 weeks of ethanol exposure and persisted after ethanol withdrawal. Use of CYP2E1-knockout mice demonstrated that ethanol-induced acetylation was not dependent solely on CYP2E1 expression. The mitochondrial content of N-AcLys-modified proteins was elevated almost 5-fold following 6 weeks of ethanol exposure. Mitochondrial content of the deacetylase Sirt3 was unchanged by 6 weeks of ethanol exposure. These data indicate ethanol intoxication changes the acetylation status of, and likely the activity of, multiple mitochondrial proteins.     

Effects of soy protein on alcoholic liver disease in rats undergoing ethanol withdrawal

ObjectiveThis investigation attempted to clarify the effects of soy protein on alcoholic liver disease (ALD) in rats undergoing ethanol withdrawal.MethodsAlcoholic liver disease was induced in rats by administration of a low-carbohydrate ethanol liquid diet for 12 weeks, after which the ethanol was withdrawn and the rats were divided into two experimental groups: a control group (EC group) and a soy protein group (EP group) for 4 weeks.ResultsAfter the 12-week ALD-inducing period, the ethanol group had significantly higher hepatic lipid accumulation, oxidative stress and inflammation. We found that the EP group had significantly lower hepatic lipids, malondialdehyde, tumor necrosis factor-α, interleukin (IL)-1β, IL-6, hydroxyproline levels and myeloperoxidase activity compared to the EC group. Moreover, the fecal total cholesterol and total lipids were higher in the EP group. Expression of the hepatic cytochrome P450 2E1 (CYP2E1) protein in the EP group was significantly lower than that in the EC group, and the hepatic peroxisome proliferator-activated receptor (PPAR) α and cytochrome P450 4A (CYP4A) protein expressions in the EP group were significantly higher than those in the EC group. In the histopathological analysis, we also found that soy protein ameliorated fat accumulation in the liver.ConclusionThese results suggest that soy protein may improve alcohol-induced lipid accumulation, oxidative stress and inflammation by decreasing proinflammatory cytokines and CYP2E1 protein expression and by increasing PPARα and CYP4A protein expressions and fecal lipid excretion, thereby producing beneficial effects on ALD during ethanol withdrawal.     

Chronic ethanol feeding inhibits plasma levels of insulin-like growth factor-1

The purpose of this study was to determine whether the generalized catabolic effects of chronic ethanol may be associated with a decline in plasma levels of insulin-like growth factor-1 (IGF-1). Male Sprague-Dawley rats were fed a liquid diet containing 5% ethanol or pair-fed a diet made isocaloric with maltose-dextrin. Animals were maintained on this diet for either 12 days or 4.5 months. Another group of animals were fed control diet ad libitum for 2 weeks. After 12 days of feeding, plasma concentrations of IGF-1 in ad libitum fed rats were 771 +/- 41 ng/ml which was greater than concentrations in either pair-fed (595 +/- 23 ng/ml) or ethanol-fed (680 +/- 40 ng/ml) rats (P less than 0.05). After 4.5 months of feeding, plasma levels of IGF-1 in ad libitum and pair-fed rats were similar to the 12 day study (736 +/- 56 and 607 +/- 26 ng/ml, respectively). However, a significant decrease in plasma levels of IGF-1 was observed in ethanol-fed animals over the 4.5 month period (551 +/- 28 ng/ml, P less than 0.05). Results of a similar study in rats fed a high-fat diet for 4.5 months were similar to those found with the low-fat diet. These results indicate that 1) dietary restriction of the type routinely used in this pair-feeding regimen decreases plasma levels of IGF-1, 2) chronic ethanol feeding further decreases plasma IGF-1 levels compared to pair-fed rats, 3) the effects of ethanol on IGF-1 concentrations are not modified by dietary fat, and 4) the effects on IGF-1 are not directly dependent on elevated plasma ethanol concentrations. Our results suggest that IGF-1 secreting cells in the liver may be progressively damaged by chronic ethanol feeding.     

Benzodiazepine - specific and nonspecific tolerance following chronic flurazepam treatment

Rats were given a flurazepam solution as their only water source for 4 weeks. The drug concentration was adjusted so the rats would consume 100–150 mg/kg daily. This treatment is known to cause a reduction in the number of specific benzodiazepine binding sites (receptor down-regulation) and tolerance to the locomotor impairment caused by the injection of a large test dose of flurazepam. Both the tolerance and the receptor down-regulation disappear within 24 hours after the end of chronic treatment. After 4 weeks of flurazepam treatment, rats were tested for locomotor impairment and loss of the righting response caused by pentobarbital, ethanol or diazepam. There was a small tolerance to pentobarbital. This lasted at least 4 days, but had disappeared by 7 days. Rats also had a small tolerance to ethanol, which disappeared between 24 and 48 hours after the end of chronic flurazepam treatment. In contrast, there was a large tolerance to diazepam, but this was gone by 24 hours after the end of chronic treatment. It appears that two types of tolerance develop during benzodiazepine treatment: (1) tolerance specific for benzodiazepines possibly mediated by receptor down-regulation, and (2) nonspecific tolerance, possibly analogous to that which develops during chronic barbiturate treatment.     

Altered behavioural adaptation in mice with neural corticotrophin-releasing factor overexpression

Overproduction of corticotrophin-releasing factor (CRF), the major mediator of the stress response, has been linked to anxiety, depression and addiction. CRF excess results in increased arousal, anxiety and altered cognition in rodents. The ability to adapt to a potentially threatening stimulus is crucial for survival, and impaired adaptation may underlie stress-related psychiatric disorders. Therefore, we examined the effects of chronic transgenic neural CRF overproduction on behavioural adaptation to repeated exposure to a non-home cage environment. We report that CRF transgenic mice show impaired adaptation in locomotor response to the novel open field. In contrast to wild-type (WT) mice, anxiety-related behaviour of CRF transgenic mice does not change during repeated exposure to the same environment over the period of 7 days or at retest 1 week later. We found that locomotor response to novelty correlates significantly with total locomotor activity and activity in the centre at the last day of testing and at retest in WT but not in CRF transgenic mice. Mice were divided into low responders and high responders on the basis of their initial locomotor response to novelty. We found that differences in habituation and re-exposure response are related to individual differences in locomotor response to novelty. In summary, these results show that CRF transgenic mice are fundamentally different from WT in their ability to adapt to an environmental stressor. This may be related to individual differences in stress reactivity. These findings have implications for our understanding of the role of CRF overproduction in behavioural maladaptation and stress-related psychiatric disorders.     

Spontaneous activity and brain 5-hydroxyindole levels measured in rats tested in two designs of elevated X-maze

The spontaneous activity of rats tested both acutely and chronically (15 minutes per day for 25 days) in an elevated X-maze composed entirely of open runways was found to be significantly less (P less than 0.01) than that measured for rats tested in a maze of similar dimensions composed entirely of enclosed runways. Acute exposure to both mazes caused significant increases (P less than 0.01) in plasma corticosterone when compared with unstressed control rats. Chronic exposure to the open, but not the enclosed maze caused a significant (P less than 0.01) attenuation of this response. Chronic exposure to the open maze caused significant increases (P less than 0.01) in the concentrations of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in hippocampus, hypothalamus and cerebral cortex when compared with unstressed control rats. When compared with the data for the rats tested repeatedly in the enclosed maze, chronic exposure to the open maze increased the 5-HT concentrations in hypothalamus (P less than 0.05) and cerebral cortex (P less than 0.01) and the 5-HIAA concentrations in hypothalamus (P less than 0.01) and hippocampus (P less than 0.01). The spontaneous locomotor activity of the rats tested in the open maze, correlated significantly (P less than 0.01) with plasma corticosterone and the 5-HIAA concentrations in hippocampus (P less than 0.01), hypothalamus (P less than 0.05) and cerebral cortex (P less than 0.01). In the rats tested in the enclosed maze, spontaneous activity only correlated significantly (P less than 0.01) with hippocampal 5-HIAA. It is concluded that the study has revealed clear differences in the behavioral, plasma corticosterone and brain 5-hydroxyindole responses to the two mazes but that the results do not provide unequivocal evidence that these differences occurred because the open maze was more aversive than the enclosed. It is also concluded that the study provides further support for the hypothesis that 5-HT turnover in the hippocampus may be directly related to the level of spontaneous locomotor activity.     

Effects of PKA modulation on the expression of neuropeptide Y in rat amygdaloid structures during ethanol withdrawal

We recently reported that neuropeptide Y (NPY) protein levels and cAMP responsive element binding (CREB) protein phosphorylation are lower in amygdaloid structures during ethanol withdrawal after chronic exposure. Furthermore, we reported that normalization of CREB phosphorylation by infusing protein kinase A (PKA) activator into the central amygdala prevents anxiety-like effects in rats during ethanol withdrawal. Here we investigated whether normalization of CREB phosphorylation by infusing PKA activator (Sp-cAMP) into the central amygdala also normalizes the expression of NPY during ethanol withdrawal. Sprague-Dawley male rats were cannulated targeting the central amygdala and then treated either with Lieber-DeCarli ethanol diet or control diet for 15 days. Subsequently ethanol-fed rats were withdrawn for 0 and 24h. The control-diet fed and ethanol-withdrawn rats were infused twice with PKA activator or inhibitor (Rp-cAMP). The protein and mRNA levels of NPY were determined in amygdaloid structures using gold-immunolabeling and the in situ RT-PCR procedure. It was found that chronic ethanol treatment has no effect on mRNA and protein levels of NPY in the central, medial, or basolateral amygdala. On the other hand, ethanol withdrawal produced significant reductions in mRNA and protein levels of NPY in the central and medial but not in the basolateral amygdala. The reductions in mRNA and protein levels of NPY were normalized in the central amygdala by infusion with PKA activator in ethanol-withdrawn rats. On the other hand, PKA-inhibitor infusion does not have any effect on mRNA and protein levels of NPY in the central amygdala of ethanol-withdrawn rats, but significantly decreased the expression of NPY in the central amygdala of control-diet fed rats. These results suggest that the decreased cellular expression of NPY in the central amygdala may play an important role in the CREB-mediated regulation of anxiety-like behaviors during ethanol withdrawal.     

急、慢性乙醇处理后大鼠伏核内cAMP反应元件结合蛋白磷酸化的变化

采用免疫组织化学的方法,检测急性、慢性乙醇作用及戒断后大鼠伏核内cAMP反应元件结合蛋白(cAMP response element binding protein,CREB)磷酸化的变化。结果显示,急性腹腔注射乙醇后15min,伏核内磷酸化CREB(Phospho-CREB,p-CREB)蛋白明显增加,30min后达高峰,至1和6h后仍明显高于对照组。而慢性饮乙醇溶液显著降低大鼠伏核内P—CREB蛋白含量,在撤除乙醇后24、72h时,伏核内p—CREB蛋白含量仍明显较低,戒断后7d,恢复到正常水平。结果表明,急性乙醇处理增加伏核内CREB磷酸化作用,而慢性乙醇作用则降低伏核内CREB磷酸化作用,这可能是乙醇依赖的分子机制之一。     

Membrane solubility of ethanol in chronic alcoholism. The effect of ethanol feeding and its withdrawal on the protection by alcohol of rat red blood cells from hypotonic hemolysis

Membranes from ethanol-fed rats are resistant to the in vitro effects of ethanol on membrane structure and function. We have proposed that the resistance arises from adaptive changes in membrane composition which lower the solubility (partition coefficient) of ethanol in these membranes. The partition of ethanol (and other alcohols and anesthetics) into red blood cells protects the cells from hypotonic hemolysis. Here, we show that the protection by alcohols and anesthetics of red blood cells from ethanol-fed rats is greatly attenuated. This finding indicates that the membrane solubility of these agents is lowered in chronic alcoholism and thus explains the resistance to the acute effects of ethanol. The protection from hemolysis decreases over 2 weeks of ethanol-feeding and returns to normal values within 1 day after ethanol withdrawal. These changes are associated with a parallel increase in total and free serum cholesterol during ethanol feeding and a return to normal values within a day after withdrawal. However, we find only a slight increase in the cholesterol/phospholipid ratio of the red blood cell membranes during the development of ethanol tolerance. In rats fed a cholesterol and saturated fat diet, the increase in serum cholesterol is also associated with an attenuation of the protection from hypotonic hemolysis.     

Hyperprolactinemia associated with chronic renal failure in the rat

Patients with CRF exhibit hyperprolactinemia and resistance to the prolactin-suppressive effects of dopamine. In order to explore the pathogenetic mechanisms involved, an animal model of CRF was developed in the adult male rat bearing an indwelling right atrial catheter by performing a two stage 5/6 nephrectomy (NX). Following NX, serum creatinine levels rose to a value of 1.36 +/- 0.2 mg/dl at 8 weeks as compared to sham-operated controls (0.31 +/- 0.1, P less than 0.01). There was a parallel increase in plasma prolactin levels in NX animals with values significantly greater than in controls by 8 weeks (49 +/- 11 vs 17 +/- 2 ng/ml, P less than 0.02). At 8 weeks, the plasma prolactin responses to metoclopramide (500 micrograms/kg, iv) were similar in unanesthetized NX and sham-operated control animals. The prolactin-suppressive effects of an iv dopamine infusion (6 micrograms/kg/min X 30 min) was also similar in the two groups (46 +/- 8% vs 40 +/- 10% suppression). The responses of lactotrophs in vitro were compared in NX and control animals at 8 weeks. Basal prolactin release during 4 h was similar in the two groups as were the suppressive responses to dopamine and bromocriptine. The results indicate that the rat with CRF, like human develops hyperprolactinemia. In contrast to the human, however, responses to dopaminergic agonists and antagonists in vivo and in vitro are unimpaired, indicating that hyperprolactinemia in rats with CRF occurs on a non-dopaminergic basis.