Effect of protein kinase C inhibition on hypoxic pulmonary vasoconstriction

The current study was done to test the hypothesis that protein kinase C (PKC) inhibitors prevent the increase in pulmonary vascular resistance and compliance that occurs in isolated, blood-perfused dog lungs during hypoxia. Pulmonary vascular resistances and compliances were measured with vascular occlusion techniques. Hypoxia significantly increased pulmonary arterial resistance, pulmonary venous resistance, and pulmonary capillary pressure and decreased total vascular compliance by decreasing both microvascular and large-vessel compliances. The nonspecific PKC inhibitor staurosporine (10^-7 M), the specific PKC blocker calphostin C (10^-7 M), and the specific PKC isozyme blocker Gö-6976 (10^-7 M) inhibited the effect of hypoxia on pulmonary vascular resistance and compliance. In addition, the PKC activator thymeleatoxin (THX; 10^-7 M) increased pulmonary vascular resistance and compliance in a manner similar to that in hypoxia, and the L-type voltage-dependent Ca²⁺ channel blocker nifedipine (10^-6 M) inhibited the response to both THX and hypoxia. These results suggest that PKC inhibition blocks the hypoxic pressor response and that the pharmacological activation of PKC by THX mimics the hypoxic pulmonary vasoconstrictor response. In addition, L-type voltage-dependent Ca²⁺ channel blockade may prevent the onset of the hypoxia- and PKC-induced vasoconstrictor response in the canine pulmonary vasculature.