α1-Adrenergic stimulation, coupled to Gq, has been shown to promote heart failure. However, the role of α1-adrenergic signaling in the regulation of myocardial contractility in failing myocardium is still poorly understood. To investigate this, we observed 1) the effect of phenylephrine on myofibrillar Ca2+ sensitivity in α-toxin-skinned cardiomyocytes, and 2) protein expression of Gq, RhoA, and myosin light chain phosphorylation using tachypacing-induced canine failing hearts. Phenylephrine significantly increased myofibrillar Ca2+ sensitivity in failing but not in normal cardiomyocytes. Whereas Y-27632 (Rho kinase inhibitor) blocked the phenylephrine-induced Ca2+ sensitization in the failing myocytes, calphostin C (protein kinase C inhibitor) had no effect on Ca2+ sensitization. The protein expression of Gαq and RhoA and the phosphorylation level of regulatory myosin light chain significantly increased in the failing myocardium. Our results suggest that α1-adrenoceptor-Gq signaling is upregulated in the failing myocardium to increase the myofibrillar Ca2+ sensitivity mainly through the RhoA-Rho kinase pathway rather than through the protein kinase C pathway.
|ジャーナル||American Journal of Physiology - Heart and Circulatory Physiology|
|出版ステータス||出版済み - 2001|
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