Effects of α₁-adrenoceptor stimulation on Mg²⁺ release in perfused guinea pig heart

관류 기니픽 심장에서 Mg²⁺ 유리에 미치는 α¹-adrenoceptor 자극효과

Recently in spite of the interest on the regulation of intracellular $Mg^{2+}$ by neurotransmitters or drugs, the magnesium ion($Mg^{2+}$) regulation by ${\alpha}_1$-adrenoceptor stimulation has not been studied in the heart yet. To elucidate the regulation of ${\alpha}_1$-adrenoceptor stimulation-induced $Mg^{2+}$ release and the effects of ${\alpha}_1$-adrenoceptor stimulation on pathophysiological conditions, in this study we have evaluated the effects of phenylephrine, PMA, $H_7$. staurosporine, verapamil and lidocaine on $Mg^{2+}$ release in perfused guinea pig heart. During preperfusion exogenous $Mg^{2+}$ was added to the medium to give 1.2mM 15min before starting to addition of drugs, and then the infusion of exogenous $Mg^{2+}$ was stopped. $Mg^{2+}$ in the perfusate leaving the heart was measured by atomic absorption spectrophotometry. $Mg^{2+}$ free solution produced an increase in heart rate and phenylephrine elicited $Mg^{2+}$ release from the heart. $Mg^{2+}$ release by phenylephrine was abolished by combined treatment with prazosin. By contrast, cardiac $Mg^{2+}$ uptake induced by a protein kinase C(PKC) activator, PMA was abolished by a selective PKC inhibitor, staurosporine. And the phenylephrine-induced $Mg^{2+}$ release was not affected by the PKC inhibitor, $H_7$. When verapamil or lidocaine was added to perfusing solution, $Mg^{2+}$ release was potentiated by phenylephrine from perfused guinea pig heart. These results suggest that ${\alpha}_1$-adrenoceptor stimulation caused $Mg^{2+}$ release and that PKC is not involved in ${\alpha}_1$-adrenoceptor mediated $Mg^{2+}$ release from perfused guinea pig heart. Under pathophysiological conditions, the $Mg^{2+}$ alteration by ${\alpha}_1$-adrenoceptor stimulation is considerable.