Seminiferous tubule fluid secretion is a Sertoli cell microtubule-dependent process inhibited by 2,5-hexanedione...

Mammalian Sertoli cells are responsible for the formation and secretion of seminiferous tubule fluid (STF) which provides the nutritional and hormonal microenvironment necessary for spermatogenesis. Exposure of rats to 2,5-hexanedione (2,5-HD) results in testicular injury characterized by a decrease of STF secretion which immediately precedes bulk germ cell necrosis. The earliest biochemical change in 2,5-HD-exposed rats is an alteration in testicular microtubule assembly kinetics. In this study, we investigate the relationship between microtubule-dependent processes and STF secretion in adult Sprague-Dawley CD rats by exposing seminiferous tubules to two types of toxicants: (1) those which alter microtubules (colchicine and 2,5-HD) and (2) an inhibitor of protein secretion (brefeldin A, [BFA]). Secretion of STF is quantitated by monitoring the rate of transport of a microinjected oil droplet in the lumen of isolated seminiferous tubules using time-lapse stereoscopic microscopy. The rate of oil droplet transport in seminiferous tubules isolated from testis pretreated in vivo for 2 hr with colchicine (40 micrograms/testis) was significantly decreased. Exposure of isolated seminiferous tubules to BFA (10 micrograms/ml) for 40 min also significantly decreased the transport of lumenal oil droplets. Exposure of rats to 1%, 2,5-HD in drinking water decreased transport of injected oil droplets in seminiferous tubules beginning at 3 weeks of exposure in the absence of significant alterations in testicular morphology. These data demonstrate that normal STF secretion requires an intact, microtubule-dependent intracellular membrane transport pathway and strengthen the association between 2,5-HD-induced disruption of Sertoli cell STF secretion and 2,5-HD-induced alterations in Sertoli cell microtubules.