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 intramuscular injection of 17 beta-estradiol, followed by intravenous injection of human chorionic gonadotropin, expressed cholesterol sulfate at a significantly high concentration. The highest concentration of cholesterol sulfate was observed 4 days after the injection of gonadotropin 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 nonpregnant endometrium was 3.2%. However, no significant change in the concentration of gangliosides was observed during the period of pseudopregnancy. In the pseudopregnant endometria, the activity of cholesterol sulfotransferase, a cytosolic thiol enzyme, was increased thirtyfold 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 arylsulfatases A and B, exhibited the same change in activity as cholesterol sulfate sulfatase. Thus, the striking increase in cholesterol sulfate after induction of pseudopregnancy was found to be due to the activation of cholesterol sulfotransferase and the simultaneous inhibition of cholesterol sulfate sulfatase.