GOSSYPOL-INDUCED APOPTOTIC DNA FRAGMENTATION CORRELATES WITH INHIBITED PROTEIN-KINASE-C ACTIVITY IN SPERMATOCYTES

After exposure of cultured rat spermatocytes to gossypol acetic acid f or five hours, DNA fragmentation in a ladder pattern was found in the medium and supernatants of cell lysates. The concentrations of gossypo l used for the induction of apoptosis ranged from 100 mu M to 300 mu M . Within this dose range, gossypol was also found to be effective at i nhibiting protein kinase C (PKC) activity. This inhibitory effect was demonstrated by measuring the PKC residing in cytosolic and particulat e fractions. However, the gossypol-induced inhibition of PKC activity was protected by phorbol 12,13-dibutyrate (PDBu), an activator of PRC. Furthermore, the presence of PDBu prevented gossypol-induced DNA frag mentation. These results suggest that spermatocyte apoptosis induced b y gossypol is correlated with the reduction of PKC activity, and that maintenance of PKC basal activity is essential for protecting the sper matocyte from apoptosis.