Sex hormones have emerged as important modulators of cardiovascular physiology and pathophysiology. Our previous studies demonstrated that testosterone increases expression and activity of L-type, voltage-gated calcium channels (Ca_v1.2) in coronary arteries of males. The purpose of the present study was to determine if testosterone (T) alters coronary PKC expression and if PKC plays a role in coronary Ca_v1.2 expression. For in vitro studies, porcine right coronary arteries (RCA) and post confluent (passages 3-6) five-day, serum restricted coronary smooth muscle cell cultures (CSMC) were incubated in the presence and absence of T or dihydrotestosterone (DHT; 10 and 100nM) for 18 hours at 37^oC in a humidified chamber. For sex and endogenous testosterone dependent effects, RCA were obtained from intact males (IM), castrated males (CM), CM with T replacement (CMT) and intact females (IF). In vitro T and DHT caused an ~2-3 fold increase in PKC protein levels, ~1.5-2 fold increase in PKC kinase activity and localization of PKC towards the plasma membrane and nuclear envelope. PKC protein levels were higher in coronary arteries of IM compared to IF. Elimination of endogenous testosterone by castration reduced RCA PKC protein levels, an effect partially (~45%) reversed by exogenous T (CMT). In CSMC, PKC inhibition with either the general PKC inhibitor, cheylerythrine, or the putative PKC inhibitor, rottlerin, completely inhibited the T-mediated increase in coronary Ca_v1.2 protein levels. Conversely, Go6976, a conventional PKC isoform inhibitor, failed to inhibit T-induced increases in coronary Ca_v1.2 protein levels. PKC siRNA completely blocked T induced increases in Ca_v1.2 protein levels in CSMC. These results demonstrate for the first time that 1) endogenous T is a primary modulator of coronary PKC protein and activity in males and 2) T increases Ca_v1.2 protein expression in a PKC dependent manner.