Steroids in Fluids and Sperm Entering and Leaving the Bovine Epididymis, Epididymal Tissue, and Accessory Sex Gland Secretions1

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Abstract
Ten steroids which may have a role in the process of sperm maturation within the epididymis were quantified by competitive protein binding or radioimmunoassay. Rete testis fluid (RTF) carrying testicular sperm into the epididymis was rich in dehydroepiandrosterone and testosterone (21 .+-. 2 and 33 .+-. 3 ng/ml), while cauda epididymal plasma (CEP) around sperm which have completed maturation had high levels of progesterone, dihydrotestosterone, 3.beta.-androstanediol, dehydroepiandrosterone and testosterone (7.4 .+-. 0.8, 20.3 .+-. 1.1, 6.5 .+-. 0.4, 8.0 .+-. 0.7 and 11.5 .+-. 0.7 ng/ml). About 4 .mu.g of steroids enter the epididymis daily in RTF, but < 1% was found in CEP; the balance presumably was absorbed by the epithelium in the proximal caput epididymidis. Nevertheless, tissue levels of total 17.beta.-OH androgens were lower in the proximal caput than in the distal caput or corpus epididymidis. In all zones of the epididymis, dihydrotestosterone accounted for about 70% of the total 17.beta.-OH androgens found in the nuclear fraction. In the cytoplasmic fraction, dihydrotestosterone predominated only in the distal caput and corpus epididymidis. In the cauda epididymidis, CEP and sperm probably accounted for < 35% of the total 17.beta.-OH androgens and < 25% of the dihydrotestosterone. The progesterone concentration of the cytoplasmic fraction was higher in the corpus and cauda than in the caput epididymidis. Twice washed testicular sperm contained more testosterone than cauda epididymal or ejaculated sperm (16.6 .+-. 1.9, 1.6 .+-. 0.2 and 1.5 .+-. 0.3 ng/109 sperm, respectively), but less progesterone (0.5 .+-. 0.1, 1.3 .+-. 0.2 and 1.0 .+-. 0.4 ng/109 sperm, respectively). As a consequence of mixture with estrogen-rich prostatic fluid (150 .+-. 9) pg/ml), ejaculated sperm contained a relatively high amount of estrogens (112 .+-. 15 pg/109 sperm). These studies revealed marked differences in steroid profiles of fluids entering and leaving the epididymis and of infertile testicular and fertile cauda epididymal sperm.