BIPHASIC C-MYC PROTEIN EXPRESSION DURING GOSSYPOL-INDUCED APOPTOSIS IN RAT SPERMATOCYTES

The presence of protooncogene products such as c-Myc proteins in rat s permatocytes has been quantitatively detected by Western immunoblot an d a computer-controlled Spot-denso-program with an IS-1000 digital ima ging system. Cellular levels of c-Myc proteins in response to gossypol were measured in spermatocytes during the process of gossypol-induced apoptosis. Within 0.5 to 2 h of the addition of gossypol, levels of c -Myc proteins fall dramatically and remain at a low level for the next several hours. The reduction in c-Myc proteins occurs 4.5-6 h before the apoptosis of spermatocytes in the presence of gossypol. Between 3 and 5 h after exposure to gossypol, the c-Myc protein content returns to preexposure (or higher) levels. In addition, the increase in c-Myc proteins occurs 1.5-4 h before the apoptotic death of spermatocytes. A n identical pattern of c-Myc protein response to gossypol was also fou nd in total testicular tissue in vitro. These results suggest that spe rmatocyte apoptosis induced by gossypol is correlated with biphasic c- Myc protein expression. This article presents some hypothetical models with which to explain c-Myc protein-mediated apoptosis. (C) 1998 Else vier Science Inc. All rights reserved.