STAGE-DEPENDENT EXPRESSION OF MESSENGER-RNA FOR CYCLIC PROTEIN-2 DURING SPERMATOGENESIS IS MODULATED BY ELONGATE SPERMATIDS

Cyclic protein 2 (CP-2) is a product of the Sertoli cell which is secr eted in a cyclical manner according to the stage of the spermatogenic cycle. This study has assessed the influence of the germ cell compleme nt on expression of CP-2 mRNA. Adult rats were treated with 650 mg/kg methoxyacetic acid (MAA) to induce the specific depletion of > 80% of pachytene and later spermatocytes from most tubules, and expression of CP-2 mRNA was then assessed at various times after treatment when par ticular germ cell types were depleted selectively. CP-2 mRNA was speci fically localised to the Sertoli cells of the seminiferous tubules by non-radioactive in situ hybridisation using a digoxigenin-labelled rib oprobe. A stage specific variation in CP-2 mRNA levels was observed, w ith the mRNA being most abundant at stages IV-VII of the spermatogenic cycle. Northern analysis revealed that treatment with MAA led to an a pparent increase in the amount of the major 1.7 kb CP-2 transcript whe n either pachytene spermatocytes or round spermatids were depleted. In contrast, the level of CP-2 mRNA was decreased by more than half at 2 1 days after MAA treatment. This decrease was confirmed by in situ hyb ridisation at 21 days after MAA treatment, when CP-2 mRNA expression w as found to be decreased or absent from tubules at stages at which CP- 2 mRNA is normally expressed (stages IV-VII) when elongate spermatids were depleted selectively from these tubules. These observations lead us to hypothesise that elongate spermatids positively modulate CP-2 mR NA expression in the Sertoli cell.