Prostaglandin F2 alpha stimulates gluconeogenesis in the perfused rat liver and this effect is blunted in livers from endotoxin infused rats

Prostaglandin F2α Facilitates Hepatic Glucose Production Through CaMKIIγ/p38/FOXO1 Signaling Pathway in Fasting and Obesity

Gluconeogenesis is drastically increased in patients with type 2 diabetes and accounts for increased fasting plasma glucose concentrations. Circulating levels of prostaglandin (PG) F_2α are also markedly elevated in diabetes; however, whether and how PGF_2α regulates hepatic glucose metabolism remain unknown. Here, we demonstrated that PGF_2α receptor (F-prostanoid receptor [FP]) was upregulated in the livers of mice upon fasting- and diabetic stress. Hepatic deletion of the FP receptor suppressed fasting-induced hepatic gluconeogenesis, whereas FP overexpression enhanced hepatic gluconeogenesis in mice. FP activation promoted the expression of gluconeogenic enzymes (PEPCK and glucose-6-phosphatase) in hepatocytes in a FOXO1-dependent manner. Additionally, FP coupled with G_q in hepatocytes to elicit Ca²⁺ release, which activated Ca²⁺/calmodulin-activated protein kinase IIγ (CaMKIIγ) to increase FOXO1 phosphorylation and subsequently accelerate its nuclear translocation. Blockage of p38 disrupted CaMKIIγ-induced FOXO1 nuclear translocation and abrogated FP-mediated hepatic gluconeogenesis in mice. Moreover, knockdown of hepatic FP receptor improved insulin sensitivity and glucose homeostasis in ob/ob mice. FP-mediated hepatic gluconeogenesis via the CaMKIIγ/p38/FOXO1 signaling pathway, indicating that the FP receptor might be a promising therapeutic target for type 2 diabetes.

cAMP-dependent signaling regulates the adipogenic effect of n-6 polyunsaturated fatty acids

The effect of n-6 polyunsaturated fatty acids (n-6 PUFAs) on adipogenesis and obesity is controversial. Using in vitro cell culture models, we show that n-6 PUFAs was pro-adipogenic under conditions with base-line levels of cAMP, but anti-adipogenic when the levels of cAMP were elevated. The anti-adipogenic action of n-6 PUFAs was dependent on a cAMP-dependent protein kinase-mediated induction of cyclooxygenase expression and activity. We show that n-6 PUFAs were pro-adipogenic when combined with a high carbohydrate diet, but non-adipogenic when combined with a high protein diet in mice. The high protein diet increased the glucagon/insulin ratio, leading to elevated cAMP-dependent signaling and induction of cyclooxygenase-mediated prostaglandin synthesis. Mice fed the high protein diet had a markedly lower feed efficiency than mice fed the high carbohydrate diet. Yet, oxygen consumption and apparent heat production were similar. Mice on a high protein diet had increased hepatic expression of PGC-1alpha (peroxisome proliferator-activated receptor gamma coactivator 1alpha) and genes involved in energy-demanding processes like urea synthesis and gluconeogenesis. We conclude that cAMP signaling is pivotal in regulating the adipogenic effect of n-6 PUFAs and that diet-induced differences in cAMP levels may explain the ability of n-6 PUFAs to either enhance or counteract adipogenesis and obesity.

The action of extracellular NAD+ on gluconeogenesis in the perfused rat liver

In the rat liver NAD+ infusion produces increases in portal perfusion pressure and glycogenolysis and transient inhibition of oxygen consumption. The aim of the present work was to investigate the possible action of this agent on gluconeogenesis using lactate as a gluconeogenic precursor. Hemoglobin-free rat liver perfusion in antegrade and retrograde modes was used with enzymatic determination of glucose production and polarographic assay of oxygen uptake. NAD+ infusion into the portal vein (antegrade perfusion) produced a concentration-dependent (25-100 microM) transient inhibition of oxygen uptake and gluconeogenesis. For both parameters inhibition was followed by stimulation. NAD+ infusion into the hepatic vein (retrograde perfusion) produced only transient stimulations. During Ca2+-free perfusion the action of NAD+ was restricted to small transient stimulations. Inhibitors of eicosanoid synthesis with different specificities (indo-methacin, nordihydroguaiaretic acid, bromophenacyl bromide) either inhibited or changed the action of NAD+. The action of NAD+ on gluconeogenesis is probably mediated by eicosanoids synthesized in non-parenchymal cells. As in the fed state, in the fasted condition extracellular NAD+ is also able to exert two opposite effects, inhibition and stimulation. Since inhibition did not manifest significantly in retrograde perfusion it is likely that the generating signal is located in pre-sinusoidal regions.

Effects of exogenous superoxide anion and nitric oxide on the scavenging function and electron microscopic appearance of the sinusoidal endothelium in the isolated, perfused rat liver

BACKGROUND/AIMS

Functional and morphological alterations of the hepatic sinusoidal endothelial cell occur in several models of experimental liver injury and in clinical settings. The causes of these alterations are multiple. The aim of this study was to test the hypothesis that the early functional impairment and morphological alterations of the sinusoidal endothelial cell and hepatic sinusoid associated with liver injury are mediated by free radical species, such as superoxide anion and nitric oxide.

METHODS

Isolated rat livers were perfused by recirculation with hemoglobin-free, Krebs-Henseleit bicarbonate buffer and presented with a source of superoxide anion (xanthine oxidase+hypoxanthine) or nitric oxide (S-nitroso-N-acetyl penicillamine). Hyaluronan uptake (an index of sinusoidal endothelial cell scavenging function), thiobarbituric acid-reactive substances content of the tissue (a marker of lipid peroxidation), reduced and oxidized glutathione (a marker of the thiol system oxidation/reduction state), lactate dehydrogenase and alanine aminotransferase activities (markers of cytolysis), as well as scanning and transmission electron microscopic appearance of the sinusoid were evaluated.

RESULTS

At the high concentrations used, both free radical generating systems suppressed hyaluronan uptake, increased malondialdehyde content of the tissue, enhanced the release of both liver enzymes, decreased the total glutathione content of the liver, and altered the ratio of reduced/oxidized glutathione. Both free radical species induced dose-dependent morphological alterations of the sinusoid, consisting of the appearance of large gaps replacing the sieve-plated fenestration.

CONCLUSIONS

The free radical species-induced functional impairment and morphological alterations of the liver sinusoid, presented in this study, closely resemble the early in vivo changes associated with liver injury under a variety of conditions, such as preservation and reperfusion, or administration of hepatotoxicants such as D-galactosamine, Gram-negative bacterial lipopolysaccharides, acetaminophen, alcohol and others. Therefore, we suggest that early liver sinusoid injury, observed under these conditions, can be attributed to the action of free radicals, such as superoxide anion and nitric oxide.

Uncoupling effects of diclofenac and aspirin in the perfused liver and isolated hepatic mitochondria of rat

Gluconeogenesis, glycolysis and glycogenolysis were studied in rat perfused liver following the infusion of various concentrations of diclofenac and aspirin, two non-steroidal anti-inflammatory drugs (NSAIDs). Glucose synthesis was measured in livers isolated from 48-h fasted rats perfused with Krebs-Henseleit bicarbonate buffer containing L-lactate (2 mM) and pyruvate (0.1 mM) as precursors. Both diclofenac (0.01-0.1 mM) and aspirin (1-10 mM) had an inhibitory effect on gluconeogenesis (GNG). The inhibition was dose-dependent and reversible. For the estimation of glycogenolysis and glycolysis, the rates of glucose release and of lactate and pyruvate production were measured in livers of well-fed rats perfused with substrate-free buffer. Infusion of diclofenac (0.1 mM) or aspirin (5 mM) strongly stimulated glycogenolysis and glycolysis (GGL/GL). In general, an increased oxygen consumption by the liver tissue was also noted in both types of experiments, as deduced from the continuous monitoring of oxygen concentration changes in the effluent. Such a pattern of response can be attributed to the uncoupling effects of the two drugs on oxidative phosphorylation. Measurements of respiration rates and membrane potential in isolated liver mitochondria submitted to various concentrations of diclofenac and aspirin confirms this assumption. Thus, 0.01 to 0.2 mM diclofenac stimulates state-4 respiration and slightly inhibits state 3, decreasing the respiratory control ratio, while the membrane potential is decreased or collapsed (depending on the drug concentration). Similar effects are recorded for aspirin at higher concentrations (0.2-5 mM), even though state 3 is not affected in this case. Arguments are presented that the concentrations of the drugs used largely correspond to the pharmacological doses employed in antipyretic and anti-inflammatory treatments. Therefore, a greater consideration should be given to the uncoupling effect, at least from the toxicological viewpoint.

Interleukin-6 tumor necrosis factor-alpha clearance and metabolism in vivo and by the isolated, perfused liver in the rat: effect of acute alcohol administration

Plasma clearance and organ distribution of intravenously injected human recombinant [125I]interleukin (IL)-6 and [125I]tumor necrosis factor (TNF)-alpha were studied in male rats, 2 hr after intravenous alcohol (ethanol) administration (single dose, 2.2 g.kg-1 body weight). Also, the rate of uptake and degradation of the two cytokines by the isolated, perfused rat liver was studied in the absence or in the presence of ethanol (35 mM) in the perfusate. Acute ethanol administration significantly increased plasma clearance rate for both cytokines (36% and 72%, for IL-6 and TNF-alpha, respectively), decreased the t1/2 alpha (30% and 11%, for IL-6 and TNF-alpha, respectively), abolished the slow (beta)-phase component for TNF-alpha, and increased t1/2 beta for IL-6 (31%). Although alcohol did not affect organ distribution of TNF-alpha, it increased the IL-6 content in the liver, kidney, and blood. IL-6 uptake rate by the isolated, perfused rat liver was 2-fold higher than TNF-alpha uptake, whereas the rate of degradation was larger for TNF-alpha than for IL-6, despite the fact that both cytokines were presented to the liver at the same concentration (6 nM). Ethanol addition to the perfusate (35 mM, final concentration) significantly increased TNF-alpha uptake (24%), without affecting IL-6 uptake or the degradation rate of either cytokine. Also, the kinetics of degradation by the isolated, perfused rat liver was linear for TNF-alpha, but exponential for IL-6. Data presented in this study demonstrate that: (1) acute alcohol consumption can alter the kinetic behavior of IL-6 and TNF-alpha in the bloodstream, mainly by accelerating their clearance which, in turn, may counteract the outcome of cytokine secretion and delivery to the blood; and (2) short exposure of liver to ethanol levels commonly seen in humans after binge drinking may alter its capacity to take up cytokines.

Tumor necrosis factor-alpha cell-surface receptors of liver parenchymal and nonparenchymal cells during acute and chronic alcohol administration to rats

Tumor necrosis factor-alpha (TNF-alpha) has been shown to contribute to the alcohol [ethanol (ETOH)]-induced alteration of hepatic function. Therefore we tested the hypothesis that the hepatic action of TNF-alpha could be due, at least in part, to alterations in TNF-alpha cell-surface receptors of hepatic parenchymal (hepatocytes) and nonparenchymal (Kupffer and sinusoidal endothelial) cells. Rats were either acutely treated with ETOH by a primed, continuous 7-hr intravenous infusion of 20% (w/v) ETOH (30 mg/100 g body weight/h) or chronically fed an ETOH-containing liquid diet (5.2% ETOH, w/v, with ETOH as 36% of total calories) for 14 weeks. Control rats in the acute group were infused with sterile saline, whereas control rats in the chronic group were fed liquid diet containing dextrin to replace ETOH in isocaloric amounts. Three hr before killing, the rats were injected intravenously with Gram-negative bacterial lipopolysaccharide [(LPS) 100 micrograms/100 g body weight] or saline. Hepatocytes, Kupffer cells, and sinusoidal endothelial cells were isolated after liver perfusion with collagenase (without pronase), separated by centrifugal elutriation, and used to determine the affinity (Kd) and capacity (Bmax) of binding sites, using recombinant human-[125I]TNF-alpha as the ligand. Two binding sites were detected on Kupffer cells and sinusoidal endothelial cells isolated from control animals: a high-affinity (Kd1, in the range of 150-200 pM), low-capacity (Bmax, in the range of 2-3 fmol/10(6) cells) binding site and a low-affinity (Kd2, in the range of 2-9 nM), high-capacity (Bmax2, in the range of 3-15 fmol/10(6) cells) binding site.(ABSTRACT TRUNCATED AT 250 WORDS)

Liver sinusoid during chronic alcohol consumption in the rat: an electron microscopic study

Transmission and scanning electron microscopic studies were performed on the liver sinusoid, with emphasis on sinusoidal endothelial cells, in rats fed a liquid diet containing either alcohol or dextrin (control) for 14 weeks. Animals were also treated with either Gram-negative bacterial lipopolysaccharide (LPS; 100 micrograms/100 g body weight, intravenously) or sterile saline (control). All specimens were prepared after perfusion fixation of the liver. Livers of rats fed dextrin-containing liquid diet displayed the ultrastructural features typical of the sinusoid and its endothelial cells. Livers from alcohol-fed animals, however, were characterized by massive loss of sieve-plate architecture of the sinusoidal endothelium, which was virtually replaced with a meshwork of enlarged openings with diameters frequently exceeding 1 micron. Morphological evidence of Kupffer cell activation could also be seen along with significant fatty infiltration of the hepatocyte. Conversely, LPS administration to dextrin-fed animals induced an apparent decrease in fenestration of the sinusoidal endothelial cell, accompanied by morphological evidence of enhanced endocytotic activity and cytoplasmic swelling. The changes seen 3 hr after LPS administration were markedly advanced at 24 hr. LPS administration to alcohol-fed rats accentuated the alterations observed after alcohol treatment alone. Additionally, the presence of platelets in the sinusoid as well as adhering to the hepatocyte microvilli in the space of Disse, along with the presence of Ito and Kupffer cell activation, greater than that observed in the alcohol-treated rats, is morphological evidence consistent with the disruption of vascular integrity in the liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of acute and chronic alcohol administration to rats on the expression of interleukin-6 cell-surface receptors of hepatic parenchymal and nonparenchymal cells

Rats were treated with alcohol either acutely (continuous, 7-hr intravenous infusion; blood alcohol levels approximately 35 mM) or chronically (liquid diet, 12-14 weeks). Three hr before killing, the animals received Gram-negative bacterial lipopolysaccharide (LPS) or saline. Hepatocytes, Kupffer cells, and liver sinusoidal endothelial cells were isolated by liver collagenase perfusion and centrifugal elutriation, and used for measurements of recombinant human [125I]interleukin-6 binding. Dissociation constant (Kd) and the amount of cell-surface receptors (Bmax) were measured on whole cells, at 4 degrees C. Two binding sites were detected on all three cell types: high-affinity (Kd1, from 20 to 125 pM) and low-affinity (Kd2, from 0.2 to 2 nM), with low Bmax (Bmax, from 0.4 to 12 fmol/10(6) cells) and high Bmax (Bmax2, from 10 to 210 fmol/10(6) cells). Hepatocytes displayed an 8-fold higher binding capacity for high-affinity sites (Bmax1) than the other two cell types. Acute ethanol treatment induced the following significant changes in the binding parameters: a decrease in Kd1 for hepatocytes and Kupffer cells, an increase in Bmax2 for hepatocytes, and a decrease in Bmax1 for Kupffer cells. Although the control (nonalcoholic) liquid diet per se completely suppressed the high-affinity binding sites, alcohol-containing diet induced only one change: a significant increase in Kd2 for hepatocytes. No changes in the binding parameters were seen after LPS administration to the chronically treated group. In the acute group, LPS mimicked alcohol action on hepatocyte binding parameters. Alcohol blunted LPS effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced response to intravenous endotoxin injections following repeated oral administration of endotoxin in the pig

Three prepubertal gilts were each given 100 mg of endotoxin (ET) in their ordinary feed rations, twice daily for 6 days; 3 other gilts received standard feed. Following ET feeding, all animals were injected intravenously (i.v.) with ET (1.0 microgram/kg b.w.) once daily for 5 days. Blood samples were collected and analysed for hematology and total serum bile acids (S-BA), glutamate dehydrogenase (S-GLDH), calcium (S-Ca), iron (S-Fe), zinc (S-Zn) and a blood plasma metabolite (15-ketodihydro-PGF2a; P-PG) of prostaglandin F2a. The animals showed no apparent clinical symptoms following ET-feeding, neither did the blood analyses reveal effects of oral ET. However, when iv ET injections were given, the ET-fed animals showed fewer clinical signs of endotoxemia following the 2nd to 5th injection. S-BA and S-GLDH increased markedly in the standard-fed group following the first injection, while the ET-fed animals showed a much smaller increase in S-BA and no change in S-GLDH on that day. The difference in response may be explained by a direct uptake of ET from the gastrointestinal tract in the ET-fed pigs, making them less sensitive to the injected ET.

Modulation of hepatic sinusoidal endothelial cell function by Kupffer cells: an example of intercellular communication in the liver

We tested the hypothesis that Kupffer cells modulate sinusoidal endothelial cell function in the liver. Rats were treated with Kupffer cell-depleting agents (gadolinium chloride and liposome-encapsulated dichloromethylene diphosphonate) or with inhibitors of phospholipase A2 or leukotriene A4 synthase (dexamethasone and diethylcarbamazine, respectively). Hyaluronan uptake by the isolated, perfused liver was measured as an index of the functional state of the sinusoidal endothelial cell. Plasma hyaluronan concentration was also determined. Three hours after Escherichia coli lipopolysaccharide administration (100 micrograms/100 gm body wt, intravenously) plasma hyaluronan levels were significantly increased (280% to 320%), whereas hepatic hyaluronan uptake was markedly decreased (approximately 76%). Pretreatment with gadolinium chloride (0.5 mg/100 gm body wt, intravenously, 21 hr before saline solution or lipopolysaccharide administration), liposome-encapsulated dichloromethylene diphosphonate (40 mumol/100 gm body wt, intravenously, 44 hr before saline solution or lipopolysaccharide injection), dexamethasone (40 micrograms/100 gm body wt, intravenously, 1 hr before saline solution or lipopolysaccharide administration) or diethylcarbamazine (repeated doses, 10 mg/100 gm body wt, intravenously, 1 hr before saline solution or lipopolysaccharide injection) counteracted the lipopolysaccharide inhibitory effect on hepatic hyaluronan uptake. With the exception of gadolinium chloride, all other agents also prevented the lipopolysaccharide-induced increase in plasma hyaluronan concentration. Gadolinium chloride only attenuated the lipopolysaccharide effect on plasma hyaluronan level. Taken together with earlier results from our laboratory, these data indicate that: (a) Kupffer cell activation by lipopolysaccharide results in suppression of hyaluronan uptake by sinusoidal endothelial cells and (b) such modulation of endothelial cell function is likely mediated by products of the lipoxygenase pathway of arachidonate metabolism.

Effect of high-dose endotoxin on glucose production and utilization

The purpose of the present study was to determine how a high dose of endotoxin (lipopolysaccharide [LPS]), which produces hypoglycemia, alters in vivo glucose uptake by individual tissues. Catheterized conscious fasted rats were injected intravenously (i.v.) with either saline, LPS (1 mg/100 g body weight [BW], lethal dose [LD] 100), or 3-mercaptopicolinic acid (3-MP), an inhibitor of gluconeogenesis. In the latter two groups, blood glucose levels were clamped at either 6 mmol/L (euglycemia) or 3 mmol/L (hypoglycemia). In the first series of experiments, whole-body glucose flux was determined using [3-3H]glucose, and in the second study in vivo glucose uptake (Rg) by individual tissues was estimated by the tracer [U-14C]-2-deoxyglucose technique. The relative contribution of hypoglycemia per se to the LPS effect was determined by comparing the values from LPS- versus 3-MP-treated animals. There was no difference in the rate of whole-body glucose utilization (Rd) between saline-infused control rats and LPS-treated animals that were hypoglycemic. However, Rg by diaphragm, spleen, liver, and lung was increased in hypoglycemic LPS-treated rats. The increased Rg in these tissues was not observed in 3-MP-treated rats with a comparable hypoglycemia. Only the gastrocnemius muscle showed a reduction in Rg under hypoglycemic conditions, and the decrease was similar in both LPS- and 3-MP-treated animals. When sufficient glucose was infused into LPS-injected rats to maintain euglycemia, whole-body glucose Rd was increased compared with that in hypoglycemic LPS-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Association of galactosamine-induced hepatitis in the rat with hyperhyaluronanaemia and decreased hyaluronan uptake by the isolated, perfused liver

Plasma hyaluronan (HA) concentration and the rate of HA uptake by the isolated, perfused liver were measured in rats treated with saline, D-galactosamine (GaI-NH2, 50 mg/100 g body wt), gadolinium chloride (GdCl3) (0.5 mg/100 g body wt), and GdCl3 + GaI-NH2. GdCl3 was given 24 hr before GaI-NH2 or saline. Plasma L-alanine:2-oxoglutarate aminotransferase (EC 2.6.1.2), a marker for hepatocyte damage, was increased by 8 hr and remained elevated for 24 hr after GaI-NH2 injection. GdCl3 did not affect plasma enzyme levels when given alone or in association with, but prior to, GaI-NH2. Plasma HA levels were increased (200%) within 24 hr after GaI-NH2 administration. A plateau was reached at 8 hr, which was maintained for at least 24 hr. Although GdCl3 alone did not affect plasma HA levels, it slightly delayed the increase in HA concentration in GaI-NH2-treated rats. Livers, isolated 24 hr after GaI-NH2 treatment, exhibited a severe depression (approximately 67%) of HA uptake. GdCl3 did not prevent this suppression. The data presented indicate that: (1) one of the sinusoidal endothelial cell-dependent functions of the liver, i.e. removal of HA from the blood stream, is profoundly impaired during galactosamine-induced hepatitis, and (2) the adverse effect of GaI-NH2 on this sinusoidal endothelial cell function may not be dependent on CdCl3-suppressible Kupffer cell functions.

Stimulation of glucose incorporation into glycogen by E-series prostaglandins in cultured rat hepatocytes

In primary cultures of rat hepatocytes, 16,16-dimethylprostaglandin E2 (16,16-dimethyl PGE2), a biologically active analogue of prostaglandin E2 (PGE2), stimulated the basal rate of [14C]glucose incorporation into glycogen. 16,16-Dimethyl PGE2 caused concentration-dependent stimulation (ED50: 10(-8) M) with a maximum 2-3 h after its addition. Prostaglandin E1 (PGE1), PGE2 and prostaglandin F2 alpha (PGF2 alpha) stimulated also the incorporation, but less effectively than 16,16-dimethyl PGE2. However, prostaglandin D2 (PGD2) did not show such effect. Cellular glycogen analysis revealed that PGE2 and 16,16-dimethyl PGE2 increased a net glycogen accumulation time-dependently. Pretreatment of the cultured hepatocytes with pertussis toxin blocked the effects of PGE2 and 16,16-dimethyl PGE2 completely and concentration-dependently. These findings indicate that E-series prostaglandins have significant effects on hepatic glycogenesis via pertussis-toxin-sensitive G protein, in addition to their inhibitory effects on hormone-stimulated glycogenolysis reported previously (Okumura, T., Sago, T. and Saito, K. (1988) Prostaglandins 36, 463-475).

Effects of acute alcohol intoxication on gluconeogenesis and its hormonal responsiveness in isolated, perfused rat liver

Rats were acutely administered ethanol as a primed constant infusion in order to produce sustained blood ethanol levels of 8-12 or 55-65 mM. At the end of ethanol infusion the livers were either freeze-clamped in vivo or isolated and perfused for metabolic studies. The rate of gluconeogenesis and its responsiveness to phenylephrine (10 microM), prostaglandin F2 alpha (5 microM) and glucagon (10 nM), as well as the redox state of the cytosolic NAD(+)-NADH system were assessed in livers isolated from acutely ethanol-treated rats, and subsequently perfused without ethanol. For liver clamped in vivo, high- but not low-ethanol treatment decreased the ATP content by 31% and slightly increased ADP and AMP content, resulting in a decreased energy charge (11%). Glutamate and aspartate content was also increased in high-dose ethanol-infused rats with no changes in malate and 2-oxoglutarate content. Gluconeogenesis with saturating concentrations of lactate (4 mM)+pyruvate (0.4 mM) was delayed in reaching a plateau in the livers of high-dose ethanol-treated rats and its response to all three stimulators was impaired. Low-dose ethanol treatment only decreased the liver response to phenylephrine. While the perfused livers of low-dose ethanol-treated rats displayed no changes in adenine nucleotide content, the livers of high-dose ethanol-treated rats had a decreased ATP (35%) and an increased AMP (77%) content, paralleled by a fall in the total adenine nucleotides (14%) and energy charge (14%). No differences were observed between the saline- and ethanol-treated rats with respect to malate-aspartate shuttle intermediate concentration in perfused livers. Also, the livers of high-, but not low-dose ethanol-treated rats had a more negative value of NAD(+)-NADH redox state as compared to the livers of control rats. The data suggest that acute ethanol intoxication produces changes in liver metabolism and its responsiveness to hormones/agonists that are demonstrable for at least 2 hr after isolation and perfusion of the liver.

Down-regulation of prostaglandin F2 alpha receptors in rat liver during chronic endotoxemia

Prostaglandin (PG) F2 alpha binding parameters were measured in purified plasma membrane preparations isolated from livers of chronically endotoxin-(ET) treated rats and corresponding controls. Two classes of binding sites were detected in both groups: high affinity, low capacity, with a KD of 44.4 +/- 8.8 nM for saline- and 28.6 +/- 11.3 nM for ET-treated rats (n = 5 for both, p greater than 0.05) and low affinity, high capacity with a KD of 1.12 +/- 0.49 microM for saline- and 1.24 +/- 0.43 microM for ET-treated rats (p greater than 0.05). Bmax values for high affinity sites were 1.01 +/- 0.18 fmol.mg-1 protein for saline- and 1.02 +/- 0.54 (same units) for ET-treated rats (p greater than 0.05). There was a significant difference (p less than 0.01) between the Bmax values for low affinity sites in saline- (675 +/- 332 fmol.mg-1 protein) and ET-treated rats (12 +/- 1, same units). This decrease in the amount of PGF2 alpha low affinity high capacity binding sites may underlie the depression of the PGF2 alpha stimulatory effect on hepatic gluconeogenesis induced by non-lethal, chronic ET treatment of rats, recently described by us (9).