Ira Weinstein

Effects of ethynyl estradiol on serum lipoprotein lipids in male and female rats

Abstract Female and male rats were administered 5 or 15 μg/kg of ethynyl estradiol in sesame oil for 14 days by subcutaneous injection, and were killed on the 15th day following a 12–14 h fasting. The very low density lipoproteins, low density lipoproteins and high density lipoproteins were isolated from the serum and the concentrations of triglyceride, cholesterol and cholesteryl esters were determined in each lipoprotein class. The concentration of triglyceride in very low density lipoprotein increased with either of the estrogen doses. Treatment with ethynyl estradiol increased the concentrations of cholesterol and cholesteryl esters in the very low density lipoprotein but decreased the concentrations of these lipids in the low density lipoprotein and high density lipoprotein. The activity of serum lecithin-cholesterol acyltransferase was increased by pretreatment with ethynyl estradiol. The secretion rates of the very low density lipoprotein triglyceride and cholesterol were measured in vivo using Triton WR-1339; ethynyl estradiol increased secretion of very low density lipoprotein lipids in both sexes. The rate of hepatic secretion of the very low density lipoprotein in females, however, exceeded that of males in control and estrogentreated animals. The concentrations of serum triglyceride were similar in untreated rats of both sexes. It is suggested that the elevated concentration of serum triglyceride, following treatment with ethynyl estradiol, results from simultaneous stimulation of hepatic production of very low density lipoprotein and peripheral utilization of the triglyceride. It is postulated that, under these conditions, production rates of very low density lipoprotein lipids exceed utilization rates. It is further postulated that the hypocholesterolemia produced by ethynyl estradiol therapy results from increased utilization of low density lipoprotein and high density lipoprotein sterol despite increased output of cholesterol in the very low density lipoprotein.

Effects of diuretic and propranolol on plasma lipoprotein lipids

Ticrynafen (TCNF), a nonthiazide diuretic, has been reported to be nonhyperlipidemic. To define the effects of these drugs on plasma lipoproteins, experiments were performed in hypertensive subjects after placebo therapy, 4 wk after therapy with either hydrochlorothiazide (HCTZ) or TCNF, 3 mo after diuretic with propranolol, and 1 mo after therapy with propranolol alone. Plasma lipoproteins were separated by ultracentrifugation and the lipid fractions isolated by extraction and silicic acid thin‐layer chromatography. Plasma low‐density lipoprotein (LDL) total cholesterol fell and high‐density lipoprotein (HDL) total cholesterol rose in subjects receiving TCNF. TCNF had no effect on plasma very low‐density lipoprotein (VLDL) triglyceride or phospholipid. There were no significant changes in LDL or HDL total cholesterol in subjects on HCTZ. HCTZ tended to increase plasma VLDL triglyceride and phospholipid. The addition of propranolol to either diuretic had no effect on LDL or HDL total cholesterol but increased VLDL triglyceride, especially in subjects on HCTZ. Propranolol alone had no effect on any of the lipids measured.

Hepatic metabolism of [1-14C]oleate in pregnancy

Livers from normal ad libitum fed nonpregnant and 20 day pregnant rats were perfused in vitro. Uptake and utilization of [1-14C]oleate were measured while the concentrations of free fatty acids in the erythrocyte-free perfusate was maintained at a steady-state level (mean 0.42 +/- 0.03 (S.E.) mM). Pregnancy increased the incorporation by the isolated liver of [1-14C]oleate into perfusate triacylglycerol and cholesteryl esters and into hepatic triacylglycerol, phospholipid, diacylglycerol and cholesteryl esters. The conversion of [1-14C]oleate by the livers into ketone bodies and CO2 was depressed by pregnancy. With pregnancy, the output of the very low density lipoprotein triacylglycerol, cholesterol, cholesteryl esters and phospholipid was increased significantly by the perfused liver. The relative molar composition of the lipid components of the very low density lipoproteins, however, was not altered by gestation, suggesting that the number of particles secreted was increased by pregnancy. The total output of glucose was decreased by livers from pregnant rats. It may be concluded from these data that livers from pregnant rats in late gestation channel fatty acid ([1-14C]oleate) preferentially into products of esterification rather than into products of oxidation.

Effects of ethynyl estradiol on incorporation of (1-14C) oleate into triglyceride and ketone bodies by the liver.

n The effect of ethinyl estradiol (EE) on the incorporation of (1-carbon-14) oleate into triglyceride and ketone bodies by the rat liver was investigated. Treatment with EE resulted in significant increases in the incorporation of oleate into hepatic (p less than .05) and perfusate (p less than .005) triglycerides. However, the incorporation of oleate into ketone body perfusate was significantly (p less than .001) reduced, though liver incorporation was not markedly affected. Liver uptake of fatty acid was somewhat lower in treated rats. Possible mechanisms for the increased rate of secretion of triglycerides following treatment with EE are briefly discussed.n

Alterations of plasma HDL lipids and apolipoproteins in female rats treated with ethynyl estradiol

Female Sprague-Dawley rats (160-200 g body weight) were injected subcutaneously daily for 14 days with 1, 5, 15, 50 or 100 micrograms ethynyl estradiol in sesame oil/kg body weight, or with oil alone. Food consumption was restricted to 15 g/day, and animals were fasted overnight before exsanguination. Concentrations of plasma cholesteryl ester decreased with increasing dosage of ethynyl estradiol, as a result of decreases in HDL cholesteryl ester. Concentrations of plasma unesterified cholesterol were not altered by treatment; the tendency for a decrement in the HDL cholesterol was not statistically significant. Plasma and HDL phospholipid also tended to decrease with increasing dose of ethynyl estradiol. Plasma levels of apolipoprotein A-I increased on treatment with 5 micrograms ethynyl estradiol/kg but were diminished at a dose of 50 micrograms ethynyl estradiol/kg. The ultracentrifugally isolated high density lipoproteins were delipidated and the distribution of apolipoproteins was characterized by SDS-polyacrylamide gel electrophoresis and esoelectric focusing. The proportion of apolipoprotein E in HDL was depressed, while apolipoprotein A-I was increased and apolipoprotein C unchanged by treatment with ethynyl estradiol. Clearly, the alterations in plasma HDL lipid levels resulting from treatment with ethynyl estradiol were accompanied by distinct changes in composition of the apolipoproteins of HDL, and a biphasic response dependent on dose of the drug. A possible mechanism for the diminution in the proportion of HDL apolipoprotein E may be the enhanced removal of the apolipoprotein E-rich (HDL1) subfraction of the HDL from the circulation on treatment with ethynyl estradiol.

Lack of effect of somatostatin on the glucagon-induced alterations of hepatic metabolism of [1-14C]oleate

Livers from normal fed male rats were perfused in a recycling system in vitro. Glucagon was infused in varying quantities to give final concentration in the cell-free perfusate of 4.9 . 10(-10)-4.9 . 10(-7) M after 3 h of perfusion, assuming no degradation of the hormone. Where indicated, cyclic somatostatin was infused simultaneously to give a final concentration of 3.0 . 10(-6) M. In the absence of somatostatin, glucagon at a concentration as low as 4.9 . 10(-10) M increased the release of glucose and increased ketogenesis, but impaired the synthesis and release of perfusate triacylglycerol and very low density lipoprotein lipids. Somatostatin did not affect these actions of glucagon. Somatostatin alone, however, did reduce the output of very low density lipoprotein. It is suggested that the alteration of fatty acid metabolism by somatostatin in vivo results from modulation of pancreatic glucagon secretion, not from interference by somatostatin of the action of glucagon on the liver.

Decreased cAMP responsiveness to glucagon in livers from ethynyl estradiol treated rats.

Abstract The effects of glucagon on the concentration and output of cAMP were studied in liver slices and in perfused livers from female rats and from animals treated with ethynyl estradiol (15 μg/kg daily for 14 days). The basal content of cAMP in liver slices, or of cAMP released into the perfusion medium in the absence of glucagon, was unaffected by prior treatment of the animal with estrogen. When glucagon was added to the medium, the concentration of cAMP in liver slices was 2.29 ± 0.32 and 1.10 ± 0.11 pmol cAMP/mg wet weight from control and ethynyl estradiol treated rats, respectively. When glucagon was added, the output of cAMP by perfused livers was maximal at 20 minutes with livers from either control or ethynyl estradiol treated rats. Output of cAMP by the perfused liver, when glucagon was added to the medium, was 8.76 ± 0.69 and 1.84 ± 0.08 nmol/g by livers from control and ethynyl estradiol treated rats, respectively. This effect was the same whether animals had been fasted for 12 hours previously, or were allowed free access to food until sacrifice. Clearly, as measured by cAMP accumulation, prior treatment of the rat with ethynyl estradiol reduced the sensitivity of the hepatic cAMP response to glucagon.

Effects of Pregnancy and Streptozotocin Diabetes on Hepatic Fatty Acid Metabolism

Abstract Nonpregnant female rats and pregnant rats were fed ad libitum. Diabetes was induced by a single intravenous injection of streptozotocin. Pregnant rats received streptozotocin on Day 17 of gestation. The diabetic rats were used 3 days after treatment with streptozotocin. Protamine zinc insulin and crystalline insulin were administered to diabetic rats subcutaneously 24 hr prior to removal of the livers for perfusion. Livers were removed and perfused in vitro in a recirculating liver perfusion apparatus. Diabetes in nonpregnant and pregnant animals decreased the output of triacylglycerol and increased ketogenesis by the isolated perfused liver in comparison to the corresponding nondiabetic group. In agreement with previous data, pregnancy increased output of triacylglycerol and decreased ketogenesis. Livers from pregnant diabetic rats secreted more triacylglycerol and fewer ketones than did livers from nonpregnant diabetic rats. Pretreatment of diabetic rats with insulin reduced ketogenesis toward normal values and increased output of triacylglycerol to values exceeding corresponding control values. Total net synthesis of triacylglycerol was increased by pregnancy and was decreased in livers from pregnant diabetic rats, when compared to their corresponding controls. The data suggest that certain hormonal changes induced by pregnancy act antagonistically to experimental insulin deficiency.