Effects of ethinylestradiol-induced cholestasis on bile flow and biliary excretion of estradiol and estradiol glucuronide by the rat

Pharmacological Characterization of a Novel Mouse Model of Cholestatic Pruritus

Patients with cholestatic liver diseases, such as primary biliary cirrhosis, usually suffer from pruritus. However, the pathogenesis of cholestatic pruritus is unclear, and there is no current effective treatment for it. In order to find a treatment for the condition, an appropriate mouse model should be developed. Therefore, here, we established a surgically-induced mouse model of cholestatic pruritus. The bile duct was ligated in order to block bile secretion from the anterior, right, and left lobes, with the exception of the caudate lobe. Serum levels of total bile acid increased after bile duct ligation (BDL). The spontaneous hind paw scratching was also increased in BDL mice. Spontaneous scratching was reduced in BDL mice by naloxone (µ-opioid receptor antagonist), U-50,488H (κ-opioid receptor agonist), and clonidine (α2-adrenoceptor agonist). Azelastine (H₁ receptor antagonist with membrane-stabilizing activity) slightly reduced scratching. However, terfenadine (H₁ receptor antagonist), methysergide (serotonin (5-HT)₂ receptor antagonist), ondansetron (5-HT₃ receptor antagonist), proteinase-activated receptor 2-neutralizing antibody, fluvoxamine (selective serotonin reuptake inhibitor), milnacipran (serotonin-noradrenalin reuptake inhibitor), and cyproheptadine (H₁ and 5-HT₂ receptor antagonist) did not affect scratching. These results suggested that partial obstruction of bile secretion in mice induced anti-histamine-resistant itching and that central opioid system is involved in cholestatic itching.

Clues to understanding the oxidation of estradiol in humans: effects of acute infectious hepatitis, autoimmune hepatitis, and chronic liver disease

Determination of 2- and 16alpha-hydroxylation of estradiol in patients with a variety of liver disorders using a dynamic method of quantitating the extent of hydroxylation revealed specific and characteristic differences in the metabolic response. Patients with acute or silent variants of hepatitis B had estrogen metabolite patterns that were indistinguishable from those found in the control subjects. Female patients with autoimmune hepatitis (formerly known as lupoid hepatitis), however, showed a moderate significant decrease (P < 0.01) in 2-hydroxylation as compared with normal controls (mean 16.3 +/- 1.9 vs. 33.9 +/- 2.5), with no significant change in 16alpha-hydroxylation. Male and female subjects with chronic alcoholic cirrhosis were almost devoid of 2-hydroxylation (mean 2.9 +/- 0.5, P < 0.01), but did show a significant increase in 16alpha-hydroxylation (P < 0.01). The results, therefore, show that the alterations in patterns of biological oxidation are highly specific and do not reflect a general inability to metabolize estrogens in the cirrhotic patient. However, the results also suggest the possibility that a substantial fraction of 16alpha-hydroxylation may occur elsewhere in the body at sites other than in the liver, explaining why this biotransformation pathway is elevated, while the reaction at C-2 is almost absent in the alcoholic cirrhotic subjects.

Pharmacology and toxicology of ethinyl estradiol and norethindrone acetate in experimental animals

For over 30 years various combinations of synthetic estrogens and progestins have been used in oral contraceptive formulations. Ethinyl estradiol (EE) and norethindrone acetate (NA) are common synthetic hormones used in oral contraceptives such as Loestrin, Brevicon, Ortho-Novum, Norlestrin, and Norinyl. In recent years these oral contraceptives have been considered for development in other therapeutic indications. Given the use of these agents for other clinical indications with different and larger target populations, an updated comprehensive review of the toxicology literature of estrogens and progestins is warranted. This review will summarize available data on the pharmacology and toxicology of estrogens and progestins with an emphasis on the specific synthetic hormones EE and NA. Ethinyl estradiol and norethindrone acetate alone or in combination, possess low acute and chronic toxicity. In some studies, EE and/or NA increased the incidence of specific tumors in susceptible strains of rodents and dogs, but not monkeys. These agents are not teratogenic when given in combination. Alone EE and NA have clastogenic properties. Overall, the animal data demonstrates that long-term exposure to EE and NA formulations pose very little health risks to humans.

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)

Subchronic toxicology of diethystilbestrol in the mouse

This study evaluated the subchronic (14-day) toxicity of selected (0.2, 1.0, and 4.0 mg/kg) daily subcutaneous injections of diethylstilbestrol (DES) in female (C57B1/6 X C3H)F1 mice. Parameters observed included body and organ weights, gross organ morphology, histopathology, clinical chemistry, and hepatic microsomal enzyme activities. The liver, bone marrow, and thymus are major target organs for DES. Liver enlargement, with associated histopathological changes consistent with mild hepatitis, centrolobular necrosis, and sinusoidal changes were observed. Supporting the histological changes were alterations in serum enzyme levels and microsomal enzyme activity. Bone marrow changes included decreases in the number of cells as well as the number of colony forming units per gram stem cells. Toxicity to the thymus was evidenced by decreased thymic weights and lymphocyte depletion. The hepatic and thymic effects were observed at the lowest (0.2 mg/kg) dose. Although all parameters were not assessed for recovery, those that were evaluated returned to control levels by thirty days after treatment.

Reversal of ethinyl estradiol-induced bile secretory failure with Triton WR-1339

The effects of Triton WR-1339 and phenobarbital on ethinyl estradiol bile secretory failure were examined to determine the mechanism responsible for decreased bile salt excretion. When administered to ethinyl estradiol-treated rats, Triton WR-1339 restored bile salt independent bile flow and maximum taurocholate transport, whereas phenobarbital corrected bile flow only. Ethinyl estradiol decreased the activities of Na(+)-K(+)-ATPase, 5'-nucleotidase, while increasing the activities of Mg(++)-ATPase and alkaline phosphatase. In contrast to these heterogeneous changes in surface membrane enzyme activities, the number and affinity of [(14)C]cholic acid carriers were not altered. When administered in vivo or added directly to surface membrane fractions Triton WR-1339 restored the activities of Na(+)-K(+)-ATPase and Mg(++)-ATPase of rats treated with ethinyl estradiol through a process that did not require protein synthesis (unaffected by cycloheximide). Phenobarbital also restored the activity of Na(+)-K(+)-ATPase to control levels, but, unlike Triton WR-1339 it did not correct the defect responsible for reduced bile salt secretion. Ethinyl estradiol increased the concentration of cholesterol esters in surface membrane fractions. When administered to ethinyl estradiol-treated rats, Triton WR-1339 restored cholesterol ester concentrations to normal, whereas phenobarbital did not. These combined data suggest that decreased or altered bile salt carriers or reduced sodium driving forces resulting from impaired activity of Na(+)-K(+)-ATPase are not responsible for decreased bile salt excretion in ethinyl estradiol-treated rats. It is proposed that the diverse changes in surface membrane function, which are associated with ethinyl estradiol bile secretory failure, may be the result of a generalized alteration in membrane lipid structure.

Alteration of bile canalicular enzymes in cholestasis. A possible cause of bile secretory failure

Bile secretory failure (cholestasis) may result from several possible mechanisms involved in bile secretion. We have examined the possibility that abnormalities in enzyme content, composition, and turnover of liver plasma membrane constituents are altered in cholestasis. Severe and mild cholestasis were produced by 5 days of bile duct ligation and ethinyl estradiol administration, respectively. Bile duct ligation but not ethinyl estradiol treatments was associated with elevations of the serum bilirubin level and 5'-nucleotidase activity. However, basal bile flow and bilirubin transport maximum (T(m)) were significantly reduced after ethinyl estradiol treatment. Liver plasma membrane fractions rich in canalicular membranes were prepared from groups of rats in each of three categories; normal, after bile duct ligation, or ethinyl estradiol administration, and their respective controls. Electron microscopy and enzyme marker studies demonstrated plasma membrane fractions free of significant contamination. Plasma membrane fractions prepared from mild as well as severe cholestasis had increased alkaline phosphatase activity, and reduced 5'-nucleotidase and Mg(2+)-ATPase activities. Co(2+)-CMPase activity was unchanged. Kinetic analysis of 5'-nucleotidase and Mg(2+)-ATPase activities in plasma membrane fractions demonstrated reduced V(maz) (but unaltered K(m)). Reducted V(maz) was unrelated to addition in vitro of di-or trihydroxy bile salts or ethinyl estradiol and, therefore, suggests that reduced activities in cholestasis are due to decreased enzyme content. Cholestasis was not associated with changes in the synthesis or degradation rate of pulse-labeled plasma membrane proteins or alterations in the major protein bands separated on sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Plasma membrane cholesterol, phospholipid, and neutral sugar content was unaltered, but sialic acid content was significantly increased in both forms of cholestasis. Alterations in specific canalicular enzymes in two forms of cholestasis suggest that these changes may be involved in the pathogenesis of bile secretory failure, or may result from cholestasis.