Tsutomu Nakahara, Kunio Ishii (*,#), Yoshio Tanaka and Koichi Nakayama
Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Shizuoka 422, Japan
(*) To whom all correspondence should be addressed.
(#) Present address: Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, 9-1 Shirokane-5, Minato-ku, Tokyo 108, Japan
Abstract: Effects of flow rate changes on nitric oxide (NO) formation in vascular endothelial cells were investigated in isolated canine mesenteric arterial bed preparations. Stepwise increases in the flow rate from 8 ml/min to 40 ml/min significantly (P<0.05) elevated perfusion pressure in a rate-dependent manner. In the presence of NG-nitro-L-arginine (L-NNA, 100 microM), perfusion pressures were significantly (P<0.01) higher than those observed under control conditions at all flow rates examined. Sodium nitroprusside (SNP) (0.1 - 10 microM) counteracted the pressor effect of L-NNA in a concentration-dependent manner. Increases in the flow rate from 10 ml/min to 40 ml/min significantly (P<0.05) augmented cyclic GMP production in the vascular bed preparation. The flow-induced cyclic GMP response was significantly (P<0.05) attenuated by L-NNA (100 microM). These results demonstrate that 1) the amount of NO released from endothelial cells toward vascular smooth muscle cells can be semi-quantified with SNP, and 2) an increase in the flow rate stimulates NO formation in endothelial cells of resistance arteries, which may play an important part in regulating systemic blood pressure.
Keywords: Canine mesenteric artery, Flow, Nitric oxide (NO), NG-nitro-L-arginine, Perfusion pressure