Histochemical localization and quantification of alpha-glucosidase in the epididymis of men and laboratory animals.

The seminal marker of epididymal function alpha-1, 4-glucosidase was localized histochemically in the cytoplasm of the efferent duct epithelium and the brush border of the entire length of the human epididymis. Quantification using the specific inhibitor castanospermine revealed strongest activity in the corpus and cauda regions. Selective inhibition of the brush border enzyme activities by maltotriose identified these as the neutral isoenzymes. Despite detection of alpha-glucosidase in the renal tubules of all the animals studied, the enzyme was not detectable in epididymides of hamsters or mice. In rabbits and monkeys, it was absent from the entire brush border but present weakly in the cytoplasm of the proximal epididymides. An enzyme distribution pattern similar to that in the human epididymis was found in rats, except for the absence of histochemical staining at pH 6.5 from the initial segment and distal cauda epididymidis. Experiments in which endogenous testosterone was depleted in rats demonstrated the dependence of epididymal alpha-glucosidase on androgen, albeit with a low sensitivity. This study suggests the rat to be a suitable model for the investigation of the role of epididymal alpha-glucosidase in fertility.