Studies of the androgen binding protein in the rete testis fluid of the ram and its relation to sexual season

Abstract

An androgen binding protein (ABP) with an electrophoretic mobility ( R f) of 0.56 is present in the rete testis fluid of adult rams. Its steroid specificity was found to be in the following order: 5α-DHT, testosterone, oestradiol-17β, dehydroepiandrosterone, 5β-DHT, androstenedione, cyproterone, cyproterone acetate, cortisol and progesterone. The characteristics of the ABP are similar to those found for the ABP of the testis and the epididymis of the rat and the rabbit. The concentration of ABP, determined by the dextran-coated charcoal method and sometimes confirmed by the steady-state polyacrylamide gel electrophoresis method, was significantly higher in the breeding season than in the non-breeding season (4.40 ± 0.98 × 10 −9 M vs. 2.60 ± 0.62 × 10 −9 M; P < 0.037). The affinity constant of the ABP was independent of the season (2.45 ± 0.21 × 10 9 M −1 vs. 2.66 ± 0.1 × 10 9 M −1 ; NS). In addition, ABP was positively correlated with 5α-DHT (r = 0.506; P < 0.0009), testosterone (r = 0.445; P < 0.0003), total protein (r = 0.329; P < 0.02) and spermatozoa ( r = 0.406; P < 0.006) in the RTF and with blood plasma testosterone (r = 0.584; P < 0.0001). Furthermore, testosterone and 5α-DHT in RTF were positively correlated (r = 0.582; P < 0.0001). These androgens were also correlated with plasma testosterone (r = 0.262, P < 0.052 for testosterone in RTF; r = 0.341, P < 0.018 for 5α-DHT). Total proteins and spermatozoa were found to be positively correlated in the RTF (r = 0.789; P < 0.0001).