On the Androgen Microenvironment of Maturing Spermatozoa^*

TLDR

Losses of androgen and ABP in the epididymal lumen may result from metabolism, diffusion, or cellular uptake. The study used in vivo micropuncture of rat reproductive tract fluids, measured testosterone, 5α‑DHT, and ABP by RIA, and calculated fluid reabsorption and sperm concentrations in the epididymis. Testosterone and 5α‑DHT concentrations decline steeply from testis to epididymis, with the highest levels in testicular interstitial fluid and caput epididymis, and 89–96 % of testicular fluid is reabsorbed, causing substantial androgen and ABP loss. Endocrinology 115: 1925–1932, 1984.

Abstract

Adult anesthetized male rats were submitted to in vivo micropuncture of the seminiferous and epididymal tubules and reproductive tract vasculature to obtain fluids for analysis of testosterone, 5α-dihydrotestosterone, and androgenbinding protein (ABP). Androgen and ABP concentrations were determined by RIA. The highest concentrations of testosterone (73.14 ± 5.12 ng/ml) were in testicular interstitial fluid. A significant downhill concentration gradient exists between testosterone concentrations in testicular interstitial fluid and seminiferous tubule fluid (50.24 ± 2.26 ng/ml); another significant decrease occurs between seminiferous tubule fluid and rete testis fluid (17.85 ± 2.11 ng/ml). 5α-Dihydrotestosterone concentrations were highest in intraluminal caput epididymidal fluids (58.73 ± 6.48 ng/ml) as were ABP concentrations (33.30 ± 2.40 μleq/μl). Intraluminal sperm concentrations were also determined, and from these data, fluid reabsorption by the efferent ducts and epididymal tubules were calculated. Eighty-nine percent of the fluid leaving the testis is reabsorbed between the rete testis and caput epididymidis, and 96% is reabsorbed between rete and cauda. It was calculated that large losses of androgen and ABP also occur from the lumen of the excurrent duct system. These losses may be due to metabolism, diffusion from the lumen, or uptake by cells. (Endocrinology115: 1925–1932, 1984)