The resorptive activity in the bull efferent ductules--a morphological and experimental study.

The resorptive activity of the efferent ductules was studied in mature and immature bulls using histochemical, electron microscopical, and experimental methods. Resorptive activity was indicated by the uptake of the protein tracer (HRP) and the presence of microvilli, endocytotic apparatus, and alkaline phosphatase activity. The above features were found in all three types of nonciliated cells, but were apparently best developed in vacuolated (type III) cells. The resorptive apparatus was fully developed by 25 weeks, an age which roughly corresponds with the luminization of seminiferous tubules and the onset of spermatogenesis. In mature bulls the resorptive apparatus was markedly affected by androgen deprivation resulting from orchidectomy and was restored by the administration of testosterone, indicating its dependence upon the circulating androgen. Efferentiectomy had little impact, indicating that the luminal androgen does not play a major role in maintaining the resorptive apparatus. The tracer study revealed that the specific granules and vacuoles of type II and III cells, respectively, are not associated with resorptive function. It also showed that the tracer injected into the rete testis took 6 to 24 hours to pass through the efferent ductules and reach the initial segment of the epididymis.