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At least 19 recordsLinked to original sources

Hepatic effect of two hypolipidemic drugs in rats.

Some hepatic effects of the hypolipidemic agents 3,9-di-3-pyridyl-2,4,8,10-tetraoxaspiro-5,5-undecane (compound A) and 2-(4-dibenzofuranyloxy)-2-methylpropionic acid (compound B) were investigated in male rats. The animals were treated orally with these drugs and a reference compound-clofibrate for 10 weeks, the daily doses being 250, 300 and 300 mg/kg body weight respectively. All three drugs caused hepatomegaly with a normal microscopic appearance in liver cells. In rats given compound A, part of some liver cells could be occupied by numerous membranes of smooth endoplasmic reticulum. The hepatocytes of the rats treated with compound B or clofibrate showed a marked increase in microbody profiles and an elevated hepatic catalase activity in comparison to the control animals. Neither the microbodies nor the catalase activity were affected by compound A. Hypolipidemic effects were demonstrated with all three compounds, the most potent activity being shown by compound B. Treatment with this agent resulted in significantly higher catalse activity than with clofibrate.

Animals

The hepatic effects of hypolipidemic drugs (clofibrate, nafenopin, tibric acid, and Wy-14,643) on hepatic peroxisomes and peroxisome-associated enzymes.

Male Swiss-Webster mice were fed diets containing four hypolipidemic agents which are known to induce proliferation of hepatic peroxisomes. Treatment with all four drugs (clofibrate; its structural analogue, nafenopin; and two drugs structurally unrelated to clofibrate, tibric acid and Wy-14,643) produced a marked hepatomegaly in the mice. The extent of the increase in liver weight correlated well with the increases in total hepatic DNA and in the collective volume of hepatocyte peroxisomes. Treatment with these drugs also produced similar increases in the activities of peroxisome-associated enzymes. The most dramatic increases were noted in the activities of the short-chain (8- to 26-fold) and medium-chain (4- to 11-fold) carnitine acyltransferase. Significant increases were also noted in the activities of catalase (twofold to threefold), alpha-glycerophosphate dehydrogenase (twofold to threefold) and the long-chain carnitine acyltransferase (twofold to fourfold). Activity of the latter enzyme, however, is not known to be associated with peroxisome fractions. Concomitant administration of actinomycin D or cycloheximide with a single oral dose of clofibrate diminished the increases in liver weight and carnitine acyltransferase which occurred with clofibrate treatment alone. The finding that the major increase in activity of peroxisome enzymes occurred in those associated with metabolism of acyl CoA groups supports the hypothesis that the hypolipidemic action of the drugs and the proliferation of hepatic peroxisomes are related functions.

Acetyltransferases

Studies on the extra-hepatic effects of glucagon in the eviscerated rat.

The in vivo effects of glucagon on the metabolism of extra-hepatic tissues have been investigated in eviscerated, functionally hepatectomized rats with intact kidneys. In these animals, even pharmacological amounts of exogenous glucagon did not significantly alter plasma glucose, FFA, or amino acids, compared with saline treatment. The possible secondary release of adrenal catecholamines following such doses of glucagon appeared to be similarly ineffective in increasing the peripheral tissue mobilization of substrates. It was only when the eviscerated animals were pretreated with insulin that the subsequent administration of glucagon or epinephrine elicited significant elevations in plasma FFA. The concomitant evisceration and adrenalectomy did not produce results which were significantly different from evisceration alone. Both kinds of animals required insulin pretreatment before a lipolytic response to glucagon or epinephrine could be demonstrated. This suggests that severe insulin insufficiency itself elicits almost maximum catabolism in these animals and that the further addition of other catabolic hormones such as glucagon or epinephrine cannot increase these catabolic effects, as manifest in plasma concentrations of FFA. These data show an extra-hepatic lipolytic effect of glucagon in vivo, but do not illuminate the significance of this effect in the intact animal.

Amino Acids

Hepatic effects of jejunoileal bypass for morbid obesity.

The most common hepatic consequence of jejunoileal bypass for morbid obesity is triglyceride accumulation (steatosis), which usually appears to be maximal during the period of acute weight loss. In certain patients, however, because of unknown factors such as the degree of steatosis, its duration, or an as yet undefined unusual patient susceptibility, probably of a metabolic nature, a chain of events is initiated which produces inflammation and fibrosis, culminating in cirrhosis. Certain analogies with alcohol-induced steatosis and its consequences are possible. Given differences between the two states for increased intracellular hepatocyte redox potential and possibly different predominant sources for fatty acid mobilization and production affecting increased intracellular triglyceride synthesis, the remainder of the pathway proposed for the development of cirrhosis from ethanolic liver disease may equally apply to the cirrhosis seen in postbypass patients. This complication, although rare (approximately 3%), has been the subject recently of more frequent reports, with death or near-death from hepatic failure. Suggested studies are indicated to support or refute the hypotheses put forward here.

Alcoholic Intoxication

Experimental galactosamine-induced hepatitis. Effect of anticoagulant and antifibrinolytic agents on microclot formation.

An experimental hepatitis was induced in rabbits by intravenous infusion of 1 g galactosamine per kilogram of body weight. Galactosamine administration caused microclot formation in kidneys, liver, lungs, and spleen in a low percentage. If, however, animals were infused with the fibrinolysis inhibitor epsilon-aminocaproic acid in addition to galactosamine, microclots were generated in a high percentage. The microclots exhibited typical staining characteristics like those observed in the generalized Shwartzman reaction. Some animals developed bilateral renal cortical necrosis. Heparin treatment prevented the occurrence of microclot fromation after galactosamine administration, but it neither prolonged the survival time of the animals nor prevented or reduced liver cell damage. Increases in serum GPT and bilirubin levels were similar in heparin-treated and untreated rabbits. The experiments indicate that disseminated intravascular coagulation is involved in galactosamine-induced hepatitis but does not contribute to the severity of the liver injury.

Alanine Transaminase

Hepatic effects of some [4-chloro-6-(2,3-xylidino)-2-pyrimidinylthio] acetic acid (WY-14,643) analogs in the mouse.

The comparative hypolipidemic and hepatic peroxisome proliferative activities of a series of thioacetic acid pyrimidines were evaluated in male mice. [4-Chloro-6-(2,3-xylidino)-2-pyrimidinylthio] acetic acid (Wy-14,643) produced significant hepatomegaly and peroxisome proliferation in liver cells. This compound also increased the hepatic catalase and carnitine acetyltransferase activities and lowered serum cholesterol and triglyceride levels. The structurally related analogs, Wy-15,690, Wy-15,672, Wy-15,746 and Wy-15,496, which lacked hypolipidemic effect failed to induce hepatomegaly and peroxisome proliferation. No substantial increase in catalase and carnitine acetyltransferase activities was noted. It is concluded that the hepatic peroxisome proliferative effect is closely related to the hypolipidemic activity, rather than to any specific chemical structure.

Animals

Hepatic effects of chlorpropamide: inhibition of glucagon-stimulated gluconeogenesis in perfused livers of fasted rats.

In perfused livers of rats fasted for 24 h, glucagon (5 x 10(-10) M) significantly elevated tissue and perfusate levels of cyclic AMP and caused a twofold increase in glucose formation from lactate. Chlorpropamide (0.8 x 10(-3) M) consistently blocked these effects. Measurements of metabolic intermediates suggest that chlorpropamide may inhibit gluconeogenesis by antagonizing the action of glucagon on the phosphoenolpyruvate cycle. In the experiments described, chlorpropamide did not lower hepatic ATP concentration or energy charge, and exerted its effects at perfusate concentrations comparable to serum concentrations reported in patients on maintenance doses of the drug.

Adenine Nucleotides

Lymphocyte cytotoxicity in chronic active hepatitis: effect of therapy and correlations with clinical and histological changes.

A study of lymphocyte cytotoxicity for rabbit hepatocyte cultures in 15 patients with untreated chronic active hepatitis showed positive results in all cases, both HBsAg positive and negative. After immunosuppressive therapy cytotoxicity became negative and remained negative, in four of nine patients followed serially. In 51 patients established on therapy for periods from three months to 12 years, cytotoxicity was negative in 19 and all patients are currently alive. However, in the remaining 32 patients in whom cytotoxicity was positive there has been a 34% mortality. Cytotoxicity remained persistently positive in 12 of 15 patients followed serially, and persistently negative in seven of nine. Cytotoxicity showed a significant association with histological disease activity, especially the extent of piecemeal necrosis, but not with biochemical tests of liver function, immunoglobulins, or autoantibodies. The basis of this cytotoxicity test is an antibody dependent cell-mediated autoimmune reaction directed against a liver specific protein, and the results suggest that in some cases immunosuppressive therapy is followed by control of this reaction. It may be possible to stop therapy in these patients, but in those in whom the reaction continues, as shown by continuing cytotoxicity, the prognosis is not as good and the use of other drug schedules would seem worthy of trial.

Adult

Gastrointestinal and hepatic effects of Amanita phalloides ingestion.

Three residents of New Jersey suddenly developed vomiting, abdominal pain, and watery diarrhea 12 h after ingesting five to 13 hand-picked Amanita phalloides-type mushrooms. The group was led by an amateur mycologist who had been eating hand-picked mushrooms without complications for 20 years. The patients developed mild to severe acute hepatic injury, with a peak serum aspartate aminotransferase level ranging from 133 to 826 Karmen U/L, and a peak serum alanine amino-transferase level ranging from 163 to 1176 Karmen U/L. One of the patients developed a transient severe coagulopathy, but no one developed renal failure or hepatic coma, and all rapidly improved. These three cases demonstrate that mycetismus can occur in the heavily urbanized northeastern United States, that consuming hand-picked mushrooms even under the guidance of an experienced amateur may be dangerous, and that Amanita phalloides ingestion produces a biphasic illness with early gastrointestinal symptoms and subsequent hepatic injury.

Abdominal Pain

Hepatic effects of endothelin. Receptor characterization and endothelin-induced signal transduction in hepatocytes.

Endothelin, a potent vasoactive peptide originally isolated from the vascular endothelial cells, exerts glycogenolytic and vasoconstrictive actions in the perfused rat liver. In this paper we demonstrate high-affinity binding sites for endothelin-1 (ET-1) on rat hepatocytes. Upon incubation at 37 degrees C, association of ET-1 with hepatocytes occurred in a time-dependent manner, was maximal between 3 and 6 h, and subsequently declined; at this temperature ET-1 was rapidly internalized with the internalized ligand exceeding the surface-bound ligand at all time points. The rate of association of 125I-ET-1 with hepatocytes was much slower when the binding assay was performed at 4 degrees C; sequestration of ET-1 in hepatocytes was also substantially reduced at this temperature. ET-1 was extremely potent in stimulating phosphoinositide metabolism in hepatocytes, with significant activation of this signal transduction process occurring at ET-1 concentrations as low as 0.1 pM, with an EC50 of 1 pM. The effect of ET-1 was coupled via a pertussis toxin-sensitive G-protein. Cholera toxin did not affect ET-1-mediated phosphoinositide metabolism and neither toxin influenced the association of 125I-ET-1 with hepatocytes. PAGE of hepatocyte membranes following exposure of the cells to 125I-ET-1 and cross-linking revealed labelling of three major proteins with apparent molecular masses of 32, 49 and 72 kDa. 125I-ET-1 labelling of each of these proteins was inhibited by unlabelled ET-1, whereas unlabelled ET-3 inhibited the labelling of only the 32 and 49 kDa proteins. 125I-ET-3 labelled the 49 kDa protein and this labelling was inhibited by both unlabelled ET-1 and ET-3. Each of these receptors appears to be functional, since both ET-1 and ET-3 stimulated phosphoinositide metabolism in hepatocytes. Down-regulation of ET-1 association and desensitization of ET-1-induced phosphoinositide metabolism occurred upon incubation of hepatocytes with the homologous ligand. Following down-regulation, the ET-1 receptor was restored to the surface of the hepatocyte by prolonged incubation, although the ET-1-stimulated phosphoinositide response remained inhibited even after complete recovery of the ET-1 association capability. These results demonstrate the presence of multiple high-affinity receptors for ET-1 on hepatocytes and the direct action of this peptide on hepatic parenchymal cells via the phosphoinositide signal transduction pathway.

Animals

Hepatic effects of xylidine isomers in rats.

The effect of repeated (4 weeks) oral administration of 2,4-, 2,5- or 2,6-xylidine (at dose levels of 400--500 mg/kg/day) on the morphology and microsomal drug metabolising enzyme activity of the liver was studied in rats. All 3 isomers caused hepatomegaly which was considered to be due to proliferation of the smooth endoplasmic reticulum. Decreases in glycogen content and glucose-6-phosphatase activity were demonstrated histochemically. Biochemical investigations showed increases in microsomal protein and cytochrome P-450 content in rats dosed with 2,4- or 2,5-xylidine and in glucuronyltransferase activity in rats given 2,4-, 2,5- or 2,6-xylidine. Aniline hydroxylase activity was increased in all treated rats except males dosed with 2,6-xylidine. The results of the study indicate that all isomes of xylidine can be inducers of microsomal drug-metabolising enzyme activity, that they may be metabolised by oxidation and that the xylidine molecule may be eliminated as a conjugate with glucuronic acid.

Aniline Compounds