부산대학교 도서관

BACKGROUND AND PURPOSE: The carbazole alkaloid murrayafoline A (MuA) enhances contractility and the Ca currents carried by the Cav1.2 channels [ICa1.2] of rat cardiomyocytes. As only few drugs stimulate ICa1.2, this study was designed to analyse the effects of MuA on vascular Cav1.2 channels. EXPERIMENTAL APPROACH: Vascular activity was assessed on rat aorta rings mounted in organ baths. Cav1.2 Ba current [IBa1.2] was recorded in single rat aorta and tail artery myocytes by the patch-clamp technique. Docking at a 3D model of the rat, α1c central pore subunit of the Cav1.2 channel was simulated in silico. KEY RESULTS: In rat aorta rings MuA, at concentrations ≤14.2 μM, increased 30 mM K-induced tone and shifted the concentration-response curve to K to the left. Conversely, at concentrations >14.2 μM, it relaxed high K depolarized rings and antagonized Bay K 8644-induced contraction. In single myocytes, MuA stimulated IBa1.2 in a concentration-dependent, bell-shaped manner; stimulation was stable, incompletely reversible upon drug washout and accompanied by a leftward shift of the voltage-dependent activation curve. MuA docked at the α1C subunit central pore differently from nifedipine and Bay K 8644, although apparently interacting with the same amino acids of the pocket. Neither Bay K 8644-induced stimulation nor nifedipine-induced block of IBa1.2 was modified by MuA. CONCLUSIONS AND IMPLICATIONS: Murrayafoline A is a naturally occurring vasoactive agent able to modulate Cav1.2 channels and dock at the α1C subunit central pore in a manner that differed from that of dihydropyridines. © 2015 The British Pharmacological Society