Ryo Saito, Kouichi Handa, Seigo Tanaka, Ai Fukumitsu, Kenji Honda, Yukio
Takano and Hiro-o Kamiya
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Fukuoka University, Jonan-ku, Fukuoka 814-0180, Japan
Abstract: Electrical field stimulation (EFS) caused biphasic relaxation, first transient and then sustained, of rat mesenteric arteries precontracted by prostaglandin (PG) F2alpha. The transient relaxation was about 45%, and the sustained relaxation was not observed after endothelium denudation of the
arteries. Nomega-Nitro-L-arginine (L-NOARG) inhibited the biphasic relaxation induced by EFS. At 1 - 100 microM, L-NOARG inhibited the transient relaxation more than the sustained relaxation. Methylene blue inhibited
the biphasic relaxation and at 100 microM, L-NOARG abolished the transient relaxation. These results suggest that the transient relaxation mainly involves nitric oxide (NO), whereas the sustained relaxation involves both NO and some other factor(s).
Keywords: Endothelium-derived relaxing factor (EDRF), Mesenteric artery, Biphasic relaxation