Effect of sex hormones on plasma cholesterol in castrated and noncastrated male rats

The administration of estradiol to both castrated and noncastrated male rats was associated with significantly increased plasma cholesterol levels as compared to controls, the estradiol in the noncastrated rats overriding the tendency of testosterone to lower plasma cholesterol.     

Age-dependent changes of rat liver plasma membrane composition

The chemical composition of liver plasma membrane was studied in Wistar rats aged between 3 and 24 months. Results obtained indicate a significant age-dependent positive correlation of both the protein: phospholipid and cholesterol: phospholipid ratios, whereas the protein: cholesterol ratio seems to remain unaffected. Phospholipid analysis of liver plasma membrane reveals that only the phosphatidylcholine content has a significant negative correlation with age; all other phospholipid species remain basically unchanged.     

Substance P and neurotensin: Opposite effects on plasma cholesterol levels in ovariectomized conscious rats

Summary Intravenous pulse injection of neurotensin produces a significant and dose-dependent increase in plasma cholesterol levels in ovariectomized conscious rats, whereas substance P has opposite effect. 4-Aminopyrazolo (3,4,-d) pyrimidine, (4-APP) also significantly lowers plasma cholesterol. The suppressive effects of both substance P and 4-APP were readily reversed by neurotensin, suggesting that the peptides act on hepatic lipoprotein secretion.Supported by grants from the Indian Council of Medical Research (ICMR), New Delhi. K.R. was recipient of a UGC fellowship.     

Alfalfa seeds: Effects on cholesterol metabolism

Summary Plasma cholesterol concentrations were reduced in 3 human volunteers during ingestion of diets containing alfalfa seeds (AS) for 3 weeks. No signs of toxicity were detected through serum determinations of multiple parameters. The ingestion of AS in rats decreased the concentration of plasma cholesterol, reduced intestinal absorption of exogenous and endogenous cholesterol, and increased fecal biliary excretion.The work described in this article, Publication No. 1082 of the Oregon Regional Primate Research Center, was supported with grants RR-00163 and HL-16587 from the National Institutes of Health.     

Effect of intralipid infusion on serum high- and low-density lipoprotein cholesterol,lecithin: Cholesterol acyltransferase,and lipoprotein lipase in tumor-bearing rats

We compared the effects of 0.45% normal saline (NS), 5% Intralipid^® (IL), and 16.7% glucose (Glu) infusions on total serum triglycerides and cholesterol, serum high-(HDL-c) and low-density lipoprotein cholesterol (LDL-c), and activity of serum lecithin: cholesterol acyltransferase (LCAT), and serum lipoprotein lipase (LPL) in rats implanted with a fibrosarcoma. In tumor-bearing rats given NS, a two-fold increase in total serum cholesterol, a four-fold increase in LDL-c, and a five-fold decrease in the HDL-c/LDL-c ratio were observed compared to tumor-free rats. In tumor-bearing rats administered IL, a two-fold increase in total serum triglyceride and cholesterol, a three-fold increase in HDL-c and HDL-c/LDL-c ratio, and a two-fold increase in LPL activity were observed compared to tumor-bearing rats administered NS. In tumor-bearing rats administered Glu, a two-fold decrease in total serum cholesterol, a two-fold decrease in HDL-c, and a three-fold decrease in LDL-c were observed compared to tumor-bearing rats administered NS. Tumor weights and LCAT activity did not differ significantly between treatment groups. Previous results have demonstrated that lipophilic compounds that interact with plasma lipoproteins have altered pharmacological effects when administered with IL. Therefore, this study suggests that IL infusions alter the HDL-c/LDL-c ratio and could affect the pharmacological behavior of anticancer compounds that predominantly distribute into the LDL fraction upon entrance into the bloodstream.     

Suppression by LH-releasing hormone (LHRH) of the augmenting effect of estradiol on the secretion of LH and FSH by the rat pituitary gland

Summary Estradiol sensitizes the pituitary gland for the gonadotropin-releasing activity of LHRH. LHRH desensitizes the pituitary gland and does so in a dose-dependent manner. Moreover, LHRH dose-dependently suppresses the sensitizing effect of EB. In rats with an LHRH concentration in the plasma of about 90 pg/ml, the sensitizing effect of estradiol is absent.     

Suppression by LH-releasing hormone (LHRH) of the augmenting effect of estradiol on the secretion of LH and FSH by the rat pituitary gland

Estradiol sensitizes the pituitary gland for the gonadotropin-releasing activity of LHRH. LHRH desensitizes the pituitary gland and does so in a dose-dependent manner. Moreover, LHRH dose-dependently suppresses the sensitizing effect of EB. In rats with an LHRH concentration in the plasma of about 90 pg/ml, the sensitizing effect of estradiol is absent.     

The effect of skim milk on plasma cholesterol in rats.

From the 15th day of birth, newborn rats were offered rat chow mixed with water or skim milk. The former also received tap water, the latter skim milk. In the latter group, plasma cholesterol was lowered in 43- and 64-day-old males and in 64-day-old females.     

Regulation of estrogen "receptors" in mammary tumors: action of prolactin in vivo

The effect of prolactin on estradiol receptors was determined in cytosol of estrogen-dependent mammary tumors of Sprague Dawley rats. Tumors were induced with 20 mg dimethylbenzanthracene, rats were ovariectomized, and the rats showing regression in tumor weight were given 1 mg sheep or rat prolactin for 5 days. Receptors were separated by dextran-charcoal and analyzed by sucrose gradient. Prolactin, milk proteins, serum proteins, and 1-alpha-feto-proteins were excluded immunologically. The estradiol receptors resembled uterine receptors in affinity, specificity, sedimentation, and nuclear transfer under estradiol influence. Castration diminished receptor content exponentially 170 f moles to 16 f moles/mg protein within 10 days; prolactin increased the number of receptors to 87 f moles compared with 15 in controls. Affinity, cellular location, and uterine receptor content were unaffected. Sheep and rat prolactin acted similarly. These results justify hypophysectomy as therapy for certain estrogen-dependent breast tumors.     

Effects of bromocriptine on plasma testosterone and gonadotropin levels and testicular lipid fractions in adult rats

Summary Bromocriptine treatment of adult male rats resulted in a decrease in testicular testosterone (T) content and a reduction in plasma T levels. This was accompanied by increase in testicular total lipids and cholesterol and depletion of testicular phospholipids.Acknowledgments. We thank Dr R. L. Elton of Sandoz Pharmaceuticals for provision of CB-154. This work was supported by the Rockefeller Foundation, New York, NY, and by NIH grants HD 12642 and P-30 HD 10202 (Radioimmunoassay Core).     

Marked elevation of HDL-cholesterol in cold-adapted golden hamsters

Golden hamsters with spontaneous hypercholesterolemia at 22 degrees C developed a further increase in plasma cholesterol when they were maintained at 6 degrees C. This hypercholesterolemia was associated with a redistribution of plasma cholesterol between VLDL and HDL. Plasma cholesterol transported in the VLDL decreased while cholesterol in the HDL increased by 45%. The LDL profile was not significantly modified.     

Marked elevation of HDL-cholesterol in cold-adapted golden hamsters

Summary Golden hamsters with spontaneous hypercholesterolemia at 22°C developed a further increase in plasma cholesterol when they were maintained at 6°C. This hypercholesterolemia was associated with a redistribution of plasma cholesterol between VLDL and HDL. Plasma cholesterol transported in the VLDL decreased while cholesterol in the HDL increased by 45%. The LDL profile was not significantly modified.     

Estrogen binds to hypothalamic nuclei of androgen-insensitive (tfm) rats

Summary Androgen-insensitive (tfm) rats possess a nuclear-estrogen binding system in the brain that is similar to that of wild-type control males. In these mutant rats, radiolabeled estradiol was bound predominantly to hypothalamic nuclei and this binding was of limited capacity.This research was supported by grants Nos HD-13957 and HD-14726 from the National Institute of Child Health and Human Development.     

Plasma lecithin: cholesterol acyltransferase activity in high-and low-responding rhesus monkeys

Summary The initial rate of esterification of plasma cholesterol by lecithin: cholesterol acyltransferase (LCAT) was measured in high- and low-responding rhesus monkeys fed a moderately high cholesterol (0.15 mg/kcal) diet. The results show that the rate of esterification of cholesterol in the plasma of the high-responders was significantly (p<0.025) higher than that of the low-responding animals. In view of known relationships between LCAT activity and plasma lipoprotein metabolism, it is suggested that the lipoprotein metabolism in the high-responders would differ from that in the low-responders.Acknowledgments. Financed by USPHS research grant HL-08974 from the National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Md.     

Plasma estradiol levels in quail during sexual development and after different estrogenic treatments]

The comparison between estradiol levels in peripheral plasma of developing quails and of estradiol benzoate treated quails (0.01, 0.02, 0.1 and 1 mg/daily/6 days) shows that only the dose of 0.01 mg reproduces the conditions of a physiological estrogen stimulation.     

Age-dependent changes of rat liver plasma membrane composition

Summary The chemical composition of liver plasma membrane was studied in Wistar rats aged between 3 and 24 months. Results obtained indicate a significant age-dependent positive correlation of both the protein:phospholipid and cholesterol:phospholipid ratios, whereas the protein:cholesterol ratio seems to remain unaffected. Phospholipid analysis of liver plasma membrane reveals that only the phosphatidylcholine content has a significant negative correlation with age; all other phospholipid species remain basically unchanged.Supported by a grant of the Italian National Research Council, Project Preventive and Rehabilitative Medicine, Subproject Mechanisms of Aging.     

Hypolipidemic effects of garlic oil in rats fed ethanol and a high lipid diet

Summary Feeding of ethanol and a high fat-high cholesterol diet to rats markedly increased the total lipids in the liver, and cholesterol and triglyceride levels in the serum, liver and kidneys. However, when ethanol mixed with 0.5% garlic oil was fed to animals maintained on the high fat-high cholesterol diet, these lipid levels were significantly reduced to levels near to those seen in untreated control rats. Garlic oil did not reduce the serum albumin or the total proteins of liver, kidneys or serum when fed along with ethanol. Probably the garlic oil enhances the catabolism of dietary cholesterol and fatty acids.The authors acknowledge with thanks the financial assistance of the University of Maiduguri for carrying out this project.     

Cholesterol feeding to rats does not modulate the expression of binding sites for HDL on liver membranes

The binding of HDL, Apo-E-free, was studied in rats fed a cholesterol rich diet for 2, 4 and 7 days. Plasma cholesterol increased up to 16-fold (from 55 to 900 mg/dl); liver cholesterol was also raised, from 0.5 to 16 mg/g of tissue. The HDL binding to membrane preparations was not affected while the binding of beta VLDL was reduced to about 50% of the controls. These data show, therefore, that liver binding sites for HDL are refractory to regulation by dietary cholesterol.     

Time-dependence of estradiol effects on protein synthesis in the rat neurohypophysis.

The incorporation of 3H-leucine into neurohypophyseal proteins was measured in vitro, 24 h after the administration of a single dose of estradiol (0.3 mug) to castrated female rats. Estradiol treatment caused a significant increase of 3H-leucine incorporation into proteins of the posterior lobe. The effects of estradiol depended largely upon time injection. Rats injected at 06.00 h, i.e., at the end of the dark period exhibited a 74% increase in protein synthesis, whereas rat injected at 14.00 h, i.e., at the middle of the light period only showed a 30% of increase.     

Cholesterol feeding to rats does not modulate the expression of binding sites for HDL on liver membranes

Summary The binding of HDL, Apo-E-free, was studied in rats fed a cholesterol rich diet for 2, 4 and 7 days. Plasma cholesterol increased up to 16-fold (from 55 to 900 mg/dl); liver cholesterol was also raised, from 0.5 to 16 mg/g of tissue. The HDL binding to membrane preparations was not affected while the binding of VLDL was reduced to about 50% of the controls. These data show, therefore, that liver binding sites for HDL are refractory to regulation by dietary cholesterol.