Protection from the effects of metabolic inhibition and reperfusion in contracting isolated ventricular myocytes via protein kinase C activation

Abstract

The protective effects of the PKC activator Phorbol 12-myristate 13-acetate (PMA) were investigated in electrically field stimulated (EFS) rat isolated ventricular myocytes following 7 min of metabolic inhibition induced by cyanide, iodoacetic acid and substrate removal, followed by reperfusion. PMA reduced reperfusion damage and increased functional recovery (response to EFS) following 10 min reperfusion from 20.0 ± 10.7% of control myocytes to 90.0 ± 7.2% following 5 min PMA pre-treatment (p<0.001). PMA significantly increased the time from the onset of MI before the myocytes failed to respond to EFS from 135 ± 19s in control cells to 200 ± 14s in PMA pre-treated cells (p<0.05). Additionally, there was an increase in the time to rigor with PMA pre-treated cells entering rigor 255 ± 17s after MI compared to 174 ±15s in control cell (p<0.05), indicating a delay in ATP depletion. During MI PMA pre-treated cells showed a significantly smaller increase in [Ca 2+]i compared to control myocytes. Following reperfusion the majority of PMA pre-treated myocytes recovered calcium transients in response to EFS and diastolic Ca 2+ levels not significantly different to those seen prior to metabolic inhibition. Activation of PKC is thought to involve translocation to the particulate fraction. Our results demonstrate the presence of PKC-α, β, γ, δ, ε, ι, λ/ζ in rat ventricular myocytes, all of which translocate to the membrane in response to PMA.