Adenosine receptor activation by R-PIA induced PKC-epsilon translocation and decreased unloaded shortening velocity in rat ventricular myocytes, an effect blocked by PKC inhibitors.
Adenosine receptor activation decreases unloaded shortening velocity in rat ventricular myocytes via phosphoinositide-PKC signaling and PKC-epsilon translocation.
We previously demonstrated that both adenosine receptor activation and direct activation of protein kinase C (PKC) decrease unloaded shortening velocity (V(max)) of rat ventricular myocytes. The goal of this study was to further investigate a possible link among adenosine receptors, phosphoinositide-PKC signaling, and V(max) in rat ventricular myocytes. We determined that the adenosine receptor agonist R-phenylisopropyladenosine (R-PIA, 100 microM) and the alpha-adrenergic receptor agonist phenylephrine (Phe, 10 microM) increased turnover of inositol phosphates. PKC translocation from the cytosol to the sarcolemma was used as an indicator of PKC activation. Western blot analysis demonstrated an increased PKC-epsilon translocation after exposure to R-PIA, Phe, and the PKC activators dioctanoylglycerol (50 microM) and phorbol myristate acetate (1 microM). PKC-alpha, PKC-delta, and PKC-zeta did not translocate to the membrane after R-PIA exposure. Finally, PKC inhibitors blocked R-PIA-induced decreases in V(max) as well as Ca(2+)-dependent actomyosin ATPase in rat ventricular myocytes. These results support the conclusions that adenosine receptors activate phosphoinositide-PKC signaling and that adenosine receptor-induced PKC activation mediates a decrease in V(max) in ventricular myocytes.
Lester et al. (Fri,) conducted a other in Rat ventricular myocytes. Adenosine receptor agonist (R-PIA) and PKC activators/inhibitors was evaluated on Unloaded shortening velocity (V(max)) and PKC translocation. Adenosine receptor activation by R-PIA induced PKC-epsilon translocation and decreased unloaded shortening velocity in rat ventricular myocytes, an effect blocked by PKC inhibitors.