Effect of ethinylestradiol and epomediol on bile flow and biliary lipid composition in rat

Prophylactic effect of resveratrol against ethinylestradiol-induced liver cholestasis

Estrogens, and particularly glucuronides such as ethinylestradiol (EE), have been shown to cause cholestasis in animal studies, by reducing bile acid uptake by hepatocytes. The aim of the present article was to investigate anticholestatic activity of resveratrol (RES) against liver cholestasis induced by EE in adult female rats. The daily oral administration of the RES at a concentration of 25 mg/kg body weight for 15 days to rats treated with EE (100 μg/kg body weight for 5 days) resulted in a significant protection against EE-induced decrease in both serum cholesterol and bile acid levels as well as against an increase of serum bilirubin concentration. The treatment also resulted in a significant increase in hepatic superoxide dismutase, glutathione peroxidase, glutathione reductase, and catalase activities as well as hepatic protein-bound and nonprotein sulfhydryl groups. RES inhibited serum alkaline phosphatase, alanine aminotransferase, pi-glutathione-S-transferase, gamma-glutamyl transpeptidase, and alpha-glutathione-S-transferase activities, as well as reduced serum tumor necrosis factor-alpha, nitric oxide, and hepatic malondialdehyde as compared to EE-treated rats. The results clearly suggest that RES has a powerful prophylactic action in cholestasis induced by EE. Taken together, RES has potential as a preventive and therapeutic agent for cholestasis and deserves clinical trial in the near future as an adjuvant therapy in women treated with estrogen.

Protective effect of Jasonia montana against ethinylestradiol-induced cholestasis in rats

Estrogens, and particularly glucuronides such as ethinylestradiol (EE), have been shown to cause cholestasis in animal studies, by reducing bile acid uptake by hepatocytes. The aim of the present article is to investigate anticholestatic activity of the ethanolic extract of the aerial parts of Jasonia montana against liver cholestasis induced by EE in adult female rats in an attempt to understand its mechanism of action, which may pave the way for possible therapeutic applications. Subcutaneous administration of 100 μg/kg b.w. ethinylestradiol to rats induced hepatocellular cholestasis with a significant decrease in serum cholesterol, bile acids and bilirubin levels as well as in hepatic superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR) activities and hepatic total, protein-bound and non-protein sulfhydryl groups. Also, treatment with EE produced significant increase in serum Pi-glutathione-s-transferase (Pi-GST), gamma glutamyl transpeptidase (γ-GT) and alpha-glutathione-s-transferase (α-GST) activities as well as serum nitric oxide (NO) and tumor necrosis factor alpha (TNF-α) level and hepatic malondialdehyde (MDA) level as compare to control group. Oral administration of the aerial parts of ethanolic extract at a concentration of 150 mg/kg b.w. daily to rats treated with EE for 15 days showed a significant protection against-induced decrease in serum cholesterol, bile acids and bilirubin levels. The treatment also resulted in a significant increase in hepatic SOD, GPx and GR activities as well as hepatic total, protein-bound and non-protein sulfhydryl groups. In addition, the extract could inhibit serum Pi-GST, γ-GT and α-GST activities as well as reduce serum TNF-α, NO and hepatic MDA as compare to ethinylestradiol treated rats. High content of flavonoids and phenolic compounds was found in ethanolic extract, which may be responsible for free radical activity. The results clearly suggest that the aerial parts of J. montana extract may effectively normalize the impaired antioxidant status in ethinylestradiol (EE)-cholestatic model. Thus the extract may have a therapeutic value in drug-induced biliary cholestasis as well as in hormonal therapy.

Evaluation of the acute and subacute toxicity of a choleretic phloracetophenone in experimental animals

Toxicity of a choleretic compound, phloracetophenone (2,4,6-trihydroxyacetophenone; THA) was investigated in mice, rats and hamsters. Acute toxicity of THA was observed to be dependent on species and route of administration, but not sex and age. LD(50) values for an acute toxicity of a single i.p. administration to adult male hamsters and mice were 338 and 365 mg/kg BW, respectively. It was significantly increased to 489 mg/kg BW in adult male rats and greatly increased by i.g. route. Subacute toxicity was investigated in adult male mice by giving THA at a doses of 37-300 mg/kg BW/day, i.g. for 30 consecutive days. High doses of THA induced periportal hepatocyte degeneration whereas plasma concentrations of alanine and aspartate aminotransferases, bilirubin, and blood urea nitrogen, and hepatic triglyceride content were only slightly increased. The possible therapeutic effect of the choleretic THA was evaluated in the ethinylestradiol (EE)-induced cholestasis. THA enhanced the hepatic clearance of sulfobromophthalein and decreased the elevated plasma alkaline phosphatase in EE-cholestatic rats to control levels. These results suggested that THA at biologically active choleretic dose had low toxicity, it might be safe for further development as a therapeutic agent for a short period of treatment in cholestasis.

Effects of epomediol on ethinyloestradiol-induced changes in glutathione homeostasis in the rat

Epomediol is a synthetic terpenoid compound that has been reported to reduce ethinyloestradiol-induced cholestasis. The choleretic action of epomediol is related to an increase in both the bile acid-dependent and independent fractions of bile flow, but the role of glutathione metabolism and transport is still unknown. This study was aimed to evaluate if changes in glutathione homeostasis could contribute to the beneficial effects of epomediol in rats with ethinyloestradiol-induced cholestasis. When compared to control animals, ethinyloestradiol treatment resulted in a significant decrease in the liver concentration of reduced (GSH) and oxidized glutathione. Both GSH and oxidized glutathione concentrations returned to normal in animals receiving ethinyloestradiol plus epomediol. Ethinyloestradiol administration induced a significant decrease in plasma and renal GSH and the tripeptide was almost absent from bile. Combined treatment with epomediol plus ethinyloestradiol normalised renal GSH and both biliary and liver cysteine were significantly increased. Liver and kidney gamma-glutamyltranspeptidase activities were higher in rats receiving ethinyloestradiol and still remained elevated in animals with the combined treatment. Liver gamma-glutamylcysteine synthetase activity rose significantly by administration of ethinyloestradiol plus epomediol but the corresponding mRNA levels were not modified. Changes in glutathione homeostasis and higher biliary levels of GSH amino acid constituents could contribute to the beneficial effects of epomediol in rats with ethinyloestradiol-induced cholestasis.

Effect of epomediol on ethinyloestradiol-induced changes in bile acid and cholesterol metabolism in rats

1. Epomediol is a terpenoid compound that has been reported to stimulate bile acid synthesis and to reverse 17alpha- ethinyloestradiol-induced cholestasis. The aim of the present study was to investigate the contribution of changes in bile acid and cholesterol metabolism to the protective effects of epomediol in ethinyloestradiol-treated rats. Animals received epomediol for 5 days at 100 mg/kg daily, i.p., ethinyloestradiol for 5 days at 5 mg/kg, s.c., or a combination of both drugs. 2. When compared with control animals, epomediol treatment resulted in a significant increase in bile flow (+42%) and in the secretion of bile acids (+74%) and cholesterol (+42%). Ethinyloestradiol administration caused a significant decrease in bile flow (-43%), bile acid secretion (-37%) and cholesterol secretion (-45%). Bile flow, bile acid secretion and cholesterol secretion were significantly increased in animals receiving ethinyloestradiol plus epomediol compared with ethinyloestradiol-treated rats (+13, +29 and +31%, respectively). 3. Both cholesterol 7alpha-hydroxylase and hydroxy-3- methylglutaryl coenzyme A reductase activities were significantly increased in epomediol-treated rats (+30 and +96%, respectively). Cholesterol 7alpha-hydroxylase activity was significantly reduced by ethinyloestradiol (-22%) and did not differ from control values in animals receiving epomediol plus ethinyloestradiol. Levels of cholesterol 7alpha-hydroxylase mRNA were elevated (+41%) by epomediol, but were not significantly modified by ethinyloestradiol or ethinyloestradiol plus epomediol. 4. It is concluded that epomediol enhances bile acid secretion by increasing the expression of cholesterol 7alpha-hydroxylase. Changes in bile acid metabolism contribute to the effects of epomediol in rats with ethinyloestradiol-induced cholestasis.

Metabolism of chylomicron cholesterol is delayed by estrogen. An in vivo study in the rat

In order to test the effects of estrogen on the clearance of cholesterol of dietary origin from the blood and its elimination from the body via the bile in an in vivo animal model, the fate of radioactivity from intravenously injected [3H]cholesterol-labeled chylomicrons was investigated in the rat. The labeled lipoproteins were administered intrajugularly to male rats previously given 17alpha ethinyl estradiol or the vehicle only, and the removal of the radioactivity from the blood and its uptake by the liver and secretion into bile was determined. Experiments were carried out in animals with or without prior drainage (20 hr) of the pool of bile acids in the enterohepatic circulation, to take account of the different demands of the liver for cholesterol in the two conditions. In rats without biliary drainage, estrogen treatment decreased the rate of removal of radioactivity from the blood by about 30% and the recovery of cholesterol in the liver by about 50% in the first 30 min after injection of the labeled chylomicrons. After biliary drainage, however, the recovery of label in the liver after 90 min was similar in estrogen-treated and control animals, although its secretion into bile was markedly reduced in the estrogen-treated group (total biliary secretion in 90 min was 26% of the value found in control rats). In addition, the apolipoprotein E (aopE) content of the serum total lipoproteins was markedly reduced by estrogen. These results provide direct evidence indicating that estrogen retards the elimination of dietary cholesterol from the body via the bile in the rat, and this is likely to be mainly due to a reduced level of apoE in chylomicrons. In view of this, we suggest that the hypothesis that estrogen increases the hepatic uptake of chylomicron cholesterol, and its excretion in the bile during contraceptive and hormone replacement therapy should be re-examined.

Hormonal regulation of sodium/sulfate co-transport in renal epithelial cells

Serum sulfate concentrations are elevated in infants, young children, and pregnant women due, at least in part, to increased renal sulfate reabsorption. Little is known about the effects of hormones, particularly those involved in growth, development, and pregnancy, on renal sulfate reabsorption. The objective of this investigation was to examine the effects of growth hormone (GH), insulin-like growth factor 1 (IGF-1), progesterone (PG), and 17beta-estradiol (EST) on renal sodium/sulfate co-transport. 35S-sulfate uptake was determined in Madin-Darby canine kidney (MDCK)/NaSi-1 cells (MDCK cells that have been stably transfected with rat sodium/sulfate co-transporter (NaSi-1) cDNA) and in opossum kidney (OK) cells. NaSi-1 mRNA was determined by RT-PCR and protein levels by ELISA. GH (0.1 nM) significantly increased the sodium/sulfate co-transport in MDCK/NaSi-1 cells up to 35%. IGF-1 induced a concentration-related stimulation of the sodium/sulfate co-transport with a maximal response observed at 1000 nM (59% increase). Sodium-dependent sulfate uptake was significantly increased when cells were preincubated with 10 nM PG, 10 nM EST, or 10 nM PG/10 nM EST up to 41%, 46%, or 39%, respectively. OK cells exhibited endogenous sodium-dependent sulfate transport; significantly increased sodium/sulfate co-transport was also observed in OK cells that were preincubated with GH, IGF-1, and PG/EST, although not with EST alone. The NaSi-1 mRNA and NaSi-1 protein levels were significantly increased in MDCK/NaSi-1 cells treated with 0.1 nM GH, 100 nM IGF-1, 10 nM PG, and/or 10 nM EST compared with control. These results suggest that the increased renal sulfate reabsorption that occurs in neonates, young and pregnant humans, and animals could be mediated by the increased steady-state levels of NaSi-1 mRNA produced by the higher plasma concentrations of GH, IGF-1, or PG/EST.

The influence of estrogen on hepatic cholesterol metabolism and biliary lipid secretion in rats fed fish oil

Both estrogen and dietary n-3 polyunsaturated fatty acids are known to be hypocholesterolemic, but appear to exert their effects by different mechanisms. In this study, the interaction between dietary fish oil (rich in n-3 polyunsaturated fatty acids) and estrogen in the regulation of hepatic cholesterol metabolism and biliary lipid secretion in rats was studied. Rats fed a low fat or a fish oil-supplemented diet for 21 days were injected with 17alpha-ethinyl estradiol (5 mg/kg body weight) or the vehicle only (control rats) once per day for 3 consecutive days. Estrogen-treatment led to a marked reduction in plasma cholesterol levels in fish oil-fed rats, which was greater than that observed with either estrogen or dietary fish oil alone. The expression of mRNA for cholesterol 7alpha-hydroxylase was decreased by estrogen in rats fed a low fat or a fish oil-supplemented diet, while the output of cholesterol (micromol/h/kg b.wt.) in the bile was unchanged in both groups. Cholesterol levels in the liver were increased by estrogen in rats given either diet, but there was a significant shift from cholesterol esterification to cholesteryl ester hydrolysis only in the fish oil-fed animals. Estrogen increased the concentration of cholesterol (micromol/ml) in the bile in rats fed the fish oil, but not the low fat diet. However, the cholesterol saturation index was unaffected. The output and concentration of total bile acid was also unaffected, but changes in the distribution of the individual bile acids were observed with estrogen treatment in both low fat and fish oil-fed groups. These results show that interaction between estrogen-treatment and dietary n-3 polyunsaturated fatty acids causes changes in hepatic cholesterol metabolism and biliary lipid secretion in rats, but does not increase the excretion of cholesterol from the body.

Impaired activity of the bile canalicular organic anion transporter (Mrp2/cmoat) is not the main cause of ethinylestradiol-induced cholestasis in the rat

To test the hypothesis that impaired activity of the bile canalicular organic anion transporting system mrp2 (cmoat) is a key event in the etiology of 17alpha-ethinylestradiol (EE)-induced intrahepatic cholestasis in rats, EE (5 mg/kg subcutaneously daily) was administered to male normal Wistar (NW) and mrp2-deficient Groningen Yellow/Transport-deficient Wistar (GY/TR-) rats. Elevated plasma bilirubin levels in GY/TR- rats increased upon EE-treatment from 65 +/- 8.4 micromol/L to 183 +/- 22.7 micromol/L within 3 days, whereas bilirubin levels remained unaffected in NW rats. Biliary bilirubin secretion was 1.5-fold increased in NW rats but remained unaltered in GY/TR- rats. Plasma bile salt concentrations remained unchanged in both strains, although hepatic levels of the sinusoidal Na+-taurocholate cotransporting protein (ntcp) were markedly reduced. Biliary secretion of endogenous bile salt was not affected in either strain. A clear reduction of mrp2 levels in liver plasma membranes of NW rats was found after 3 days of treatment. The bile salt-independent fraction of bile flow (BSIF) was reduced from 2.6 to 2.0 microL/min/100 g body weight in NW rats with a concomitant 62% reduction of biliary glutathione secretion. The absence of mrp2 and biliary glutathione in GY/TR- rats did not prevent induction of EE-cholestasis; a similar absolute reduction of BSIF, i.e., from 1.1 to 0.6 microL/min/100 g bodyweight, was found in these animals. EE treatment caused a reduction of the maximal biliary secretory rate (S(RM)) of the mrp2 substrate, dibromosulphthalein (DBSP), from 1,040 to 695 nmol/min/100 g body weight (-38%) in NW rats and from 615 to 327 nmol/min/100 g body weight (-46%) in GY/TR- rats. These results demonstrate that inhibition of mrp2 activity and/or biliary glutathione secretion is not the main cause of EE-induced cholestasis in rats. The data indicate that alternative pathways exist for the biliary secretion of bilirubin and related organic anions that are also affected by EE.

Enhanced biliary excretion of canalicular membrane enzymes in ethynylestradiol-induced cholestasis. Effects of ursodeoxycholic acid administration

Cholestasis is associated with a marked increase in the release of canalicular membrane enzymes into bile. This phenomenon has been related to an increased lability of these canalicular membrane integral proteins to the solubilizing effects of secreted bile salts. To further characterize the effects of oral ursodeoxycholic acid (UDCA) administration on ethynylestradiol (EE)-induced cholestasis, the influence of this bile acid on changes in biliary excretion of membrane-bound enzymes was investigated. Bile flow, basal bile salt and biliary lipid secretory rates, the maximum secretory rate of taurocholate (TC SRm), and the biliary excretion of the canalicular membrane-bound ectoenzymes alkaline phosphatase (ALP) and gamma-glutamyl transpeptidase (GGT) were measured in rats after EE and/or UDCA administration. The activities of ALP, GGT and Na+,K(+)-ATPase in purified isolated canalicular and sinusoidal membrane fractions and the ultrastructure of hepatic acinus, including histochemical studies of ALP distribution, were also examined. EE significantly reduced bile flow, bile salt and biliary lipid secretory rates, and TC SRm, and caused dilatation and loss of microvilli at the canalicular pole of hepatocytes. Biliary excretion of ALP increased 2-fold, whereas biliary excretion of GGT was unchanged. The relationship between biliary excretion of ALP or GGT and bile salt secretion (units of enzyme activity secreted per nanomole of bile salt) was greater in EE-treated rats compared with controls (2.1- and 1.5-fold greater for ALP and GGT, respectively), indicating that in EE-induced cholestasis more enzyme was released into bile per nanomole of bile salt. Na+,K(+)-ATPase activity in sinusoidal membrane fraction was reduced significantly, whereas ALP activity increased in both membrane fractions in EE-treated rats. The histochemical distribution of ALP in the acinus showed a strong reaction in acinar zone 3 and at both the canalicular and sinusoidal membranes. Oral administration of UDCA prevented EE-induced bile secretory failure by normalizing bile flow, bile salt and biliary phospholipid secretory rates, and TC SRm. UDCA also prevented the EE-induced changes in the biliary excretion of enzymes. On the contrary, UDCA did not modify either the enzyme activity in isolated membrane fractions or the morphological or ALP histochemical changes associated with EE administration. These data indicate that in EE-induced cholestasis changes occur at the canalicular membrane, enabling this portion of the plasma membrane to be more susceptible to the solubilizing effect of bile salt, and that oral administration of UDCA prevents bile secretory failure and changes in the biliary excretion of ALP and GGT in EE-treated rats.

Hepatoprotection in ethinylestradiol-treated rats is provided by tauroursodeoxycholic acid, but not by ursodeoxycholic acid

Ursodeoxycholic acid (UDCA) and tauroursodeoxycholic acid (TUDCA) have been suggested as potential treatments for drug-induced cholestasis. It was therefore decided to study the effects of administration of UDCA or TUDCA on individual serum bile acid concentration, conventional liver tests and associated hepatic ultrastructural changes in ethinylestradiol-treated (EE) rats mg/kg per day). Control rats were treated s.c. with propylene glycol. EE-treated rats were randomly assigned to receive daily i.p. injections of placebo, TUDCA or UDCA. Four rats in each group were treated for 4 consecutive days, and a second four for 14 days. After 4 days of treatment, the serum levels of cholic acid and taurocholic acid were significantly increased in EE-treated rats. None of the conventional liver tests were significantly different among the four groups. After 14 days of treatment the serum levels of cholic acid, chenodeoxycholic acid, glycocholic acid, glycochenodeoxycholic acid, taurocholic acid, taurochenodeoxycholic acid, bilirubin, alkaline phosphatase and gamma glutamyltransferase were significantly raised in EE and EE plus UDCA treated rats. EE plus TUDCA treated rats, however, had no significant changes in these individual serum bile acids or conventional liver tests. The ultrastructure of livers from EE plus TUDCA treated rats was similar to those of controls. On the other hand, EE and EE plus UDCA rats both showed a significant reduction in sinusoidal microvilli. These results show that treatment of rats for 4 days with EE induces significant rises in the serum concentrations of two individual bile acids and that TUDCA protects against this.(ABSTRACT TRUNCATED AT 250 WORDS)

Type II crigler-Najjar syndrome with intrahepatic cholestasis

A 58-year-old Japanese man was admitted to our hospital with appendicitis and marked unconjugated hyperbilirubinemia (11.6 mg/dl). The jaundice worsened following appendectomy, and the direct-reacting bilirubin increased, probably due to the ceftizoxime administered postoperatively. Bilirubin diglucuronide was the main component of the serum direct-reacting bilirubin (51%) in serum measured by liquid chromatography. Because the discontinuation of ceftizoxime did not markedly improve the jaundice, epomediol, 200 mg tid, was administered orally. There was a marked decrease of serum bilirubin with an increase in the delta bilirubin/(conjugated bilirubin + delta bilirubin) ratio. After improvement of jaundice to below the pre-surgical level (4.4 mg/dl), we analyzed the duodenal bile for bilirubin fractions; those showed a marked reduction in bilirubin diglucuronide and a marked increase in bilirubin monoglucuronide, which was consistent with type II Crigler-Najjar syndrome. A marked increase of bilirubin diglucuronide in serum of this patient during cholestasis suggests that bilirubin conjugation proceeds in this syndrome when excretion of conjugated bilirubin decreases.

Organic solvents increase membrane fluidity and affect bile flow and K+ transport in rat liver

Following the earlier observation that inhalation of volatile lipid solvents and of narcotic gases causes cholestasis, we studied the effects of various organic solvents on bile flow, plasma membrane fluidity and potassium movement in rat liver. Both in vivo and in the isolated perfused liver, applications of CCl4, CHCl3, dichloromethane, trichloroethylene, halothane, benzene and cyclohexane elicited rapid and sustained but reversible cholestasis. A transient phase of choleresis was observed prior to and after cholestasis, during the increase and fall in liver tissue solvent concentrations, respectively. Tissue concentrations required to produce cholestasis were lower the higher the lipophilicity of the solvent. Membrane fluidity was measured in isolated basolateral liver cell membranes by fluorescence polarization. Fluidity increased with increasing solvent concentration, the increase being associated with either biphasic stimulation and inhibition of membrane enzymes (Na+,K(+)-ATPase, 5'nucleotidase) or with inhibition alone (Mg(2+)-ATPase). In the isolated perfused liver, application of organic solvents caused hepatic uptake of K+ that was followed by K+ release upon withdrawal of the solvent. The magnitude of K+ uptake elicited by the solvent was comparable with the effect of blocking K+ channels with 2 mM Ba2+, but Ba2+ was ineffective in the presence of the solvent. In contrast, application of ouabain caused K+ release in equal amounts in the absence and presence of the solvent, indicating that K+ uptake elicited by the solvent results from inhibition of K+ efflux through K+ channels rather than stimulation of the Na+,K+ pump. The data show that cholestasis elicited by lipid solvents is associated with an increase in membrane fluidity and with disturbance of liver K+ homeostasis. The significance of these observations is discussed with respect to other models of experimental cholestasis.