Protein kinase C-ε primes the cardiac sarcolemmal adenosine triphosphate-sensitive potassium channel to modulation by isoflurane

Abstract

Background: Cardioprotection by volatile anesthetic-induced preconditioning is known to involve intracellular signaling pathways. Recent studies have shown that protein kinase C (PKC) plays an important role in anesthetic-induced preconditioning. In this study, the effects of the activation of specific isozymes of PKC, specifically PKC-ε and -δ, on the modulation of the sarcolemmal adenosine triphosphate-sensitive potassium (sarcK ATP) channel by isoflurane were investigated. Methods: The sarcK ATP current was measured in ventricular myocytes isolated from guinea pig hearts using the whole cell configuration of the patch clamp technique. Peptides that induced the translocation of specific PKC isozymes were used to activate PKC-ε and PKC-δ. Results: Under whole cell conditions, isoflurane alone was unable to elicit the opening of the sarcK ATP channel. Pretreatment with the specific PKC-ε activator, PP106, primed the sarcK ATP channel to open in the presence of isoflurane. The resulting sarcK ATP current densities in the presence of 0.88 mM isoflurane were 6.5 ± 6.0 pA/pF (n = 7) and 40.4 ± 18.2 pA/pF (n = 7) after pretreatment with 100 and 200 nM PP106, respectively. The PKC-ε antagonist PP93 abolished this effect. A scrambled peptide of the PKC-ε activator PP105 did not prime the sarcK ATP channel. The PKC-δ activator PP114 was significantly less effective hi priming the sarcK ATP channel. 5-Hydroxydecanoate significantly attenuated the effect of the PKC-ε activator on the sarcK ATP channel. In addition, immunohistochemical analysis showed that the PKC-ε isoform translocated to both the mitochondria and sarcolemma after anesthetic-induced preconditioning, whereas the PKC-δ isoform translocated to the mitochondria. Conclusion: The PKC-ε isozyme primed the sarcK ATP channel to open in the presence of isoflurane. The PKC-δ isozyme was significantly less effective in modulating the isoflurane effect on this channel.