Identification of stage-specific changes in protein secretion by isolated seminiferous tubules from the rat following exposure to either m-dinitrobenzene or nitrobenzene.

The objective of this study was to identify effects of two known Sertoli cell toxicants on the secretion of proteins by seminiferous tubules (ST) isolated from adult rats at different stages of the spermatogenic cycle and cultured in vitro for 24 hr with [35S]methionine. Adult rats received a single oral dose of 50 mg/kg metadinitrobenzene (m-DNB) or 300 mg/kg nitrobenzene (NB). Long lengths of ST at stages II-V, VI-VIII or IX-XII were then isolated from control and treated rats at 1 or 3 days post-treatment; selection of stages was based on the stage specificity of the early (24-72 hr) adverse effects of m-DNB and NB on spermatogenesis in vivo. In addition, ST at the same stages were isolated from untreated rats and cultured in the presence or absence of m-DNB or NB (10(-4)M). Incorporation of [35S]methionine into secreted proteins was assessed and the pattern of protein secretion evaluated using two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (2-D SDS-PAGE). ST isolated from rats pretreated 24 hr earlier with NB in vivo showed a significant decrease in the overall incorporation of [35S]methionine into secreted proteins at stages VI-VIII and IX-XII, whereas ST at stages II-V showed no such change; comparable protein changes were observed when 10(-4) M NB was added in vitro for 24 hr to ST isolated at the same stages from untreated rats.(ABSTRACT TRUNCATED AT 250 WORDS)