Effects of endothelin-1 on the myogenic contraction of canine cerebral artery in response to quick stretch

The present study was performed to investigate the effects of endothelin-1 (ET-1) on the myogenic contraction in response to mechanical stimulation in cerebral artery. Quick stretch at a rate of 10 cm/sec with the amount of: 10-40% of the initial muscle length (=100%) produced a myogenic contraction in canine cerebral artery. ET-1 at 30 pM, which itself produces a small co ntraction corresponding to about 15% of the maximal response, potentiated s tretch-induced contraction. By contrast, ET-1 at concentrations over 100 pM suppressed the stretch-induced tone. The potentiated component of stretch- induced tone in the presence of 30 pM ET-1 was largely attenuated by Ca2+ c hannel blockers, nimodipine (1 muM) or diltiazem (1 muM). These findings su ggest that lower concentrations (pM range) of ET-1 potentiates myogenic ten sion development of cerebral artery in response to mechanical stretch possi bly via an increased Ca2+ influx through voltage-gated Ca2+ channel.