Protein kinase Cε contributes to regulation of the sarcolemmal Na+-K+ pump

A reduction in angiotensin II (ANG II) in vivo by treatment of rabbits with the angiotensin-converting enzyme inhibitor, captopril, increases Na+-K+ pump current (I-p) of cardiac myocytes. This increase is abolished by exposure of myocytes to ANG II in vitro. Because ANG II induces translocation. of the F-isoform. of protein kinase C (PKC epsilon), we examined whether this isozyme regulates the pump. We treated rabbits with captopril, isolated myocytes, and measured I-p of myocytes voltage clamped with wide-tipped patch pipettes. I-p of myocytes from captopril-treated rabbits was larger than I-p of myocytes from controls. ANG II superfusion of myocytes from captopril-treated rabbits decreased I-p to levels similar to controls. Inclusion of PKC epsilon -specific blocking peptide in pipette solutions used to perfuse the intracellular compartment abolished the effect of ANG II. Inclusion of psi epsilon RACK, a PKC epsilon -specific activating peptide, in pipette solutions had an effect on I, that was similar to that of ANG Il. There was no additive effect of ANG II and psi epsilon RACK. We conclude that PKC epsilon regulates the sarcolemmal Na+-K+ pump.