抄録
In ventricular myocytes, α1-adrenoceptor stimulation (α1ARS) increases L-type Ca2+ current (ICa,L) in perforated patch clamp (PP) recording but not in conventional whole cell recording. We hypothesized Ca2+-related protein kinase such as Ca2+/calmodulin-dependent protein kinase II (CaMKII) or protein kinase C (PKC) is involved in the regulation of ICa,L during α1ARS. In this study, we investingated the effect of phenylephrine (Phe) on ICa,L in adult rat ventricular myocytes using PP recording. As previous studies, we observed biphasic modulation in ICa,L by 10 μM Phe; a transient decrease followed by a sustained increase. However, 1 μM Phe just increased ICa,L. In the presence of CaMKII inhibitor 0.5 μM KN-93, a CaMKII inhibitor, 10 μM Phe produced only a sustained negative phase of ICa,L while 1 μM Phe did not alter ICa,L. In the presence of 10 μM chelerythrine, a PKC inhibitor, 10 μM Phe produced only a sustained negative phase as in the presence of CAMKII inhibitor. Our result suggests that (1) the effect of α1ARS on ICa,L can be classified into two phases (negative phase and positive phase) which have different concentration-dependence and (2) CaMKII and PKC regulate the positive phase of ICa,L during α1ARS. [Jpn J Physiol 54 Suppl:S96 (2004)]
