Phorbol ester regulates the abundance of enkephalin precursor mRNA but not of amyloid beta-protein precursor mRNA in rat testicular peritubular cells.

Cultured peritubular cells prepared from the testes of 20-day-old rats contained both preproenkephalin (A) mRNA (1.5 kb) and amyloid beta-protein precursor mRNA (3.6 and 2.8 kb). The phorbol ester TPA and forskolin (an adenylate cyclase activator) increased the preproenkephalin mRNA abundance to 9.0 and 5.8 times the control, respectively. TPA alone had no effect on the intracellular cAMP level. A combination of TPA and forskolin elicited a synergistic increase in the ppEnk mRNA abundance over 30-fold. Dexamethasone potentiated the effect of forskolin but not of TPA. These results suggest that TPA regulates the preproenkephalin mRNA abundance through a cAMP-independent pathway. In contrast, TPA, forskolin, and dexamethasone showed little or no effect on the abundance of amyloid beta-protein precursor mRNA.