Effects of castration and testosterone administration on serum lipoproteins and their apoproteins in male spontaneously hypertensive rat.

Serum triglyceride and very low density lipoprotein (VLDL) concentrations were higher in male spontaneously hypertensive rat than in male control Wistar Kyoto rat, whereas serum cholesterol, phospholipids, and high density lipoprotein (HDL) concentrations were lower. Castration of hypertensive rats induced an increase in serum cholesterol, phospholipids, and HDL, and a decrease in serum triglyceride and VLDL. The cholesterol content of HDL increased, whereas the triglycerides decreased after gonadectomy of hypertensive rats. These changes in serum lipids and lipoproteins could be reversed by the administration of testosterone. Apolipoprotein E contents in VLDL and HDL of hypertensive rats were low when compared with control rats but rose after castration and could be reduced by testosterone administration. Hypertensive rats accumulated triglycerides and cholesterol in the liver, which resulted in an increase of liver weight. Castration reduced the hepatic lipids as well as liver weight. The effects of castration and testosterone treatment on lipids and lipoproteins were more prominent in spontaneously hypertensive rats than in control rats. These results suggest that testosterone reduces VLDL catabolism which is related to changes of apolipoprotein composition, and that hypertensive rats are more sensitive to testosterone than control rats.