Secretion of proteins and glycoproteins by perifused rabbit corpus epididymal tubules: effect of castration.

Protein synthesis in epididymal tissue of intact and castrated rabbits was studied after incubation of epididymal minces with [35S]-cysteine or [35S]-methionine and protein separation by two-dimensional gel electrophoresis. Regional differences in the pattern of protein synthesized were observed. Castration did not change overall protein synthesis, but it reduced these regional differences. The presence of 5 alpha-DHT in the culture medium of the proximal corpus epididymidis perfused for 24 hr did not increase overall protein synthesis in tubules from intact or castrated rabbits and did not reinitiate synthesis of the proteins that had disappeared after castration. The kinetics of glycoprotein synthesis and secretion were studied by light and electron microscopy autoradiography at 0.5, 2, 6, and 24 hr after exposure to [3H]-mannose, [3H]-fucose, and [3H]-glucosamine. Changes in the distribution of mannose- and glucosamine-labeled material indicated that the decline in grain density over the epithelium from 30 min to 24 hr coincided with an increasing reaction over the stereocilia border from 30 min to 2 hr and in the lumen from 2 to 24 hr. The distribution of fucose-labeled material indicated that the grain reaction over the epithelium declined more rapidly than with the mannose label. When the glucosamine-labeled sperm mass was released from the tubules, the labeled material was lost after the first washing, indicating that the glucosamine-labeled glycoproteins did not bind firmly to corpus spermatozoa within 24 hr. After castration, both mannose- and fucose-labeled materials migrated to the cell apex more rapidly than in the intact animal, but they were not released as readily into the lumen. The culture of epididymal tubules from castrated males with 5 alpha-DHT for 24 hr did not promote the release of either mannose- or fucose-labeled material into the lumen. However, testosterone given in vivo for 2 weeks restored secretion of mannose-labeled material into the lumen.