BINDING OF SEX STEROIDS TO RABBIT SPERM

Abstract

Semen from rabbits treated with 3H-estradiol was radioactive. Seminal fluids contained an average of 66.8% of the activity while twice-washed sperm had 11.2%. Comparison of binding capacity in vitro of tritiated sex steroids showed that progesterone and estradiol had a much greater affinity (P<T .05) for sperm than did testosterone (11.1, 7.8 and 1,1%, respectively). An increase in incubation time from 30 min. to 20 hr. did not significantly alter the amounts of steroid bound to sperm. The amount of steroid bound to washed sperm was increased 3-fold by delaying steroid incubation until after removal of sperm from seminal fluids. Attempts to remove significant amounts of 3h-steroids from sperm by incubation of each sample with 10 times the amount of cold steroid were unsuccessful. Autoradiographs of sperm labeled in vitro with 3h-estradiol revealed grains located primarily on the periphery of the sperm cell, which indicates attachment and not penetration of the steroid.