Hypoxic preconditioning upregulates K-ATP channels through activation of protein kinase C in rat ventricular myocytes

AIM: To test: 1) if hypoxic preconditioning upregulates the activity of K-A TP channels in isolated adult rat cardiac myocytes; 2) if the upregulation involves protein kinase C (PKC). METHODS: By the whole-cell patch-clamp rec ording technique, K-ATP channel currents (I-KATP) were measured in the card iomyocytes with no pretreatment (CON), hypoxic exposure preceding reoxygena tion (HPC), phorbol 12-myristate 13-acetate (PMA), and chelerythrine additi on with HPC (CH + HPC), respectively. RESULTS: At 0 mV and 5 min after 2, 4 -dinitrophenol (DNP) perfusion, the membrane currents for the CON, HPC, PMA , and CH + HPC were (3.5 +/- 1.9), (7.7 +/- 1.5), (7.5 +/- 3.3), (4.6 +/- 2 .4) nA, respectively. Compared with the CON, the I-KATP in the HPC and PMA were significantly augmented (P < 0.01) while the I-KATP in the CH + HPC re mained similar to the CON(P > 0.05). CONCLUSION: I) hypoxic preconditioning stimulated the activity of PKC and markedly enhanced the activity of K-ATP channels in the isolated rat cardiac myocytes; 2) PKC activation was invol ved in the upregulation of K-ATP channels.