Effects of Ca²⁺ on protein kinase C activation in atrial natriuretic peptide regulation

심방 이뇨호르몬의 분비조절에서 Ca²⁺이 protein kinase C 활성화에 미치는 영향

Atrial natriuretic peptide(ANP) is a hormone with potent natriuretic, diuretic and relaxing properties on vascular smooth muscle. Specific chemical modulator in response for the ANP secretion has not been found yet. Therefore, we have investigated the role of $Ca^{2+}$ responsible for the regulation of ANP induced by protein kinase C(PKC) on mechanically stretch-induced ANP secretion in the rat atria. The results obtained were as follows ; 1. ANP secretion and ANP concentration were increased to more in $Ca^{2+}$-free buffer than in the Kreb-Henseleit buffer on mechanically stretch-induced ANP secretion(p < 0.05), but extracellular fluid translocation(ECF) was not significant. Phorbol 12-myristate 13-acetate(PMA, $10^{-7}M$) induced ANP secretion and ANP concentration in $Ca^{2+}$-free buffer shown to more accentuate on mechanically stretch-induced ANP secretion than in the $Ca^{2+}$-free buffer(p < 0.05), but ECF translocation was not significant. 2. In the presence of ryanodine($3{\times}10^{-6}M$), PMA($10^{-7}M$) induced ANP secretion and ANP concentration in the Kreb-Henseleit buffer were shown to more increase on mechanically stretch-induced ANP secretion than in the ryanodine($3{\times}10^{-6}M$) with the Kreb-Henseleit buffer(p < 0.05), but ECF translocation was not significant. 3. In the presence of ryanodine($3{\times}10^{-6}M$), PMA($10^{-7}M$) induced ANP secretion and ANP concentration in the $Ca^{2+}$-free buffer was shown to more increase on mechanically stretch-induced ANP secretion than in the ryanodine($3{\times}10^{-6}M$) with the $Ca^{2+}$-free buffer on mechanically induced ANP secretion(p < 0.05), but ECF translocation was not significant. The results suggest that PKC-induced ANP secretion may not be related to the change of $Ca^{2+}$ on mechanically induced ANP secretion in the rat atria.