Effects of Sex Hormones on Rat Lipoproteins*

Sex hormones (and/or gender) have marked effects on the production and catabolism of plasma lipoproteins in several species. The aim of this work was to characterize the composition and density distribution of the plasma lipoproteins of male and female rats in some detail and to ascertain whether some of the changes seen in plasma were due to hormone action on the liver. Young adult male and female rats of the same age fed a high carbohydrate diet were studied. Experimental animals were castrated. Some animals of each sex were treated with injections of estradiol cypionate (E2, 2.5 μg/day) or testosterone propionate (Tp; 200 μg/day). These injections restored plasma hormone levels of castrated rats to physiological ranges. Controls, sham operated or castrated, were injected with sesame oil. Levels of triglycerides, cholesterol, apoprotein A-I (ApoA-I), ApoB, ApoC-III3, and lipoproteins with densities less than 1,065 in plasma were similar in all groups, but high density lipoproteins (HDL) levels were high...