Steroid receptors in the canine epididymis

High-affinity and low-capacity molecules that bind 5 alpha-dihydrotestosterone and oestradiol-17 beta have been demonstrated in the canine epididymis. The molecules were shown to be proteinaceous in nature, thermolabile and sedimented in a sucrose density gradient with a coefficient of 8S with respect to bovine serum albumin. Only minor differences were found for dissociation constants for oestradio-17 beta (3.5 +/- 1.74 S 10(-10) M) and 5 alpha-dihydrotestosterone (4.2 +/- 10.75 X 10(-10) M) (means +/- s.d.) in the three anatomically distinct regions of the epididymis.