Identification of stage-specific changes in protein secretion by isolated seminiferous tubules from rats following exposure to short-term local testicular heating

Abstract

The objective of this study was to identify the early (after 4 and 24 h) effects of short-term local testicular heating (43°C for 30 min) on the secretion of proteins by seminiferous tubules isolated from adult rats at stages II-V, VI-VIII or IX-XII of the spermatogenic cycle, and cultured in vitro for 24 h with [35S]methionine. Incorporation of [35S]methionine into secreted and intracellular proteins was assessed and the pattern of protein secretion was evaluated using two-dimensional SDS-PAGE. Seminiferous tubules isolated from control rats exhibited the characteristic, androgen-dependent increase in protein secretion at stages VI-VIII. At 4 h after exposure to local testicular heating, seminiferous tubules at these stages showed a significant increase (P<0.001) in the overall incorporation of [35S]methionine into secreted proteins, whereas seminiferous tubules at stages II-V and IX-XII showed no significant change. In marked contrast, seminiferous tubules isolated from rats 24 h after local testicular heating showed a significant decrease in the incorporation of [35S]methionine into secreted proteins at stages VI-VIII (P < 0.001) and to a lesser extent at IX-XII (P < 0.05), whereas seminiferous tubules at stages II-V showed no change in incorporation. Prior treatment to maintain normal intratesticular concentrations of testosterone in heat-exposed rats failed to prevent these changes. Similar results were obtained when incorporation of [35S]methionine into intracellular proteins was evaluated 4 and 24 h after exposure to local testicular heating. Analysis of seminiferous tubule-secreted proteins by two-dimensional SDS-PAGE identified three androgen-regulated proteins that showed reproducible decreases in secretion following exposure to local testicular heating. These results suggest that changes in overall protein secretion by seminiferous tubules may explain some of the adverse effects of heat on the testes.