[Comparison between the effects of (-)- and (+)-gossypol on protein kinase C and protein kinase A].

Protein kinase C(PKC) and protein kinase A(PKA) purified from rat liver were incubated with (-)- and (+)-gossypol. The activity of PKC was significantly inhibited in a concentration-dependent manner by both (-)-gossypol and (+)-gossypol. (-)-gossypol was found to inhibit type I PKA, whereas the inhibitory action of (+)-gossypol for type I PKA was less potent. Both (-)-gossypol and (+)-gossypol showed inhibition for type II PKA only at high concentration. These results suggest that administration of gossypol might impair cellular signal transduction.