PSEUDOPREGNANCY-DEPENDENT ACCUMULATION OF CHOLESTEROL SULFATE DUE TO UP-REGULATION OF CHOLESTEROL SULFOTRANSFERASE AND CONCURRENT DOWN-REGULATION OF CHOLESTEROL SULFATE SULFATASE IN THE UTERINE ENDOMETRIA OF RABBITS

The uterine endometria of rabbits induced into pseudopregnancy by intr amuscular injection of 17 beta-estradiol, followed by intravenous inje ction of human chorionic gonadotropin, expressed cholesterol sulfate a t a significantly high concentration. The highest concentration of cho lesterol sulfate was observed 4 days after the injection of gonadotrop in for formation of the corpus luteum, being 10 times higher than that in nonpregnant endometria, and 15.2% of the total cholesterol in the endometrium was converted to the sulfated form, whose percentage in no npregnant endometrium was 3.2%. However, no significant change in the concentration of gangliosides was observed during the period of pseudo pregnancy. In the pseudopregnant endometria, the activity of cholester ol sulfotransferase, a cytosolic thiol enzyme, was increased thirtyfol d over that in the nonpregnant endometria, whereas cholesterol sulfate sulfatase, a microsomal enzyme, exhibited approximately one-tenth of the activity in nonpregnant endometria. Arylsulfatase C, but not aryls ulfatases A and B, exhibited the same change in activity as cholestero l sulfate sulfatase. Thus, the striking increase in cholesterol sulfat e after induction of pseudopregnancy was found to be due to the activa tion of cholesterol sulfotransferase and the simultaneous inhibition o f cholesterol sulfate sulfatase.