Mechanism of endothelium-dependent relaxation induced by substance P in the coronary artery of the pig.
1. Using front-surface fluorometry of fura-2-loaded porcine coronary arterial strips with the endothelium intact, we investigated the mechanisms of vasorelaxation induced by substance P (SP). Fura-2 fluorescence signals which indicated the cytosolic Ca2+-concentration ([Ca2+]i), were observed to arise exclusively from teh smooth muscle cells in these strips. 2. During the contractions induced by U46619 (100 nM), a thromboxane A2 analogue, an SP-induced endothelium-dependent, biphasic vasorelaxation was observed, which consisted of an initial rapid relaxation phase followed by a sustained phase, with a transient decrease in [Ca2+]i. Pretreatment with indomethacin (Ind) had no effect on the SP-induced relaxation; however, pretreatment with NG-nitro-L-arginine (L-NOARG) partially, but significantly inhibited the decrease in both the [Ca2+]i and tension abolished. Thus, part of the relaxation was considered to be mediated by L-NOARG-sensitive relaxing factor (endothelium-derived relaxing factor: EDRF). 3. During the 40 mM K+-depolarization-induced contraction which may eliminate the effects of endothelium-derived hyperpolarizing factor (EDRF), the vasorelaxation reduced by SP was completely inhibited by L-NOARG. 4. During the vasorelaxation induced SP, the [Ca2+]i-tension relationships shifted to the right of the contractions induced by either U46619 or high K+-depolarization. 5. Using front-surface fluorometry of fura-2 loaded porcine aortic valvular strips, we examined the effects of SP on [Ca2+]i in endothelial cells in situ. SP induced a rapid increase in [Ca2+]i of endothelial cells in situ followed by a small sustained phase in normal PSS (5.9 mM K+). The increase in extracellular K+ had no apparent effect on the SP-induced [Ca2+]i elevation of endothelial cells.
Kuroiwa
M
M
Division of Molecular Cardiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Aoki
H
H
Kobayashi
S
S
Nishimura
J
J
Kanaide
H
H
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000704:Analysis of Variance; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001685:Biological Factors / Q000378:metabolism; D003331:Coronary Vessels / Q000187:drug effects* / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D005470:Fluorometry; D016257:Fura-2 / Q000737:chemistry; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D019335:Nitroarginine; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology; D013373:Substance P / Q000494:pharmacology*; D013552:Swine; D013928:Thromboxane A2 / Q000031:analogs & derivatives / Q000494:pharmacology; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D001685:Biological Factors; D011450:Prostaglandin Endoperoxides, Synthetic; D014662:Vasoconstrictor Agents; C067410:endothelium-dependent hyperpolarization factor; D019335:Nitroarginine; D013373:Substance P; D013928:Thromboxane A2; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D001120:Arginine; D019001:Nitric Oxide Synthase; D016257:Fura-2