title: Pharmacologic characteristics of non-prostanoid, non-nitric oxide mediated and endothelium-dependent relaxation of guinea-pig aorta in response to substance P.
abstract: The pharmacologic characteristics of the non-prostanoid (prostacyclin, PGI2), non-nitric oxide (NO) mediated endothelium-dependent relaxation in response to substance P were examined in the guinea-pig aorta. Substance P, in a concentration-dependent manner, relaxed the ring preparations of guinea-pig thoracic aorta preconstricted with norepinephrine (NE) in an endothelium-dependent manner. Substance P-induced endothelium-dependent relaxation was not affected by indomethacin (3 x 10(-6) M) as in the case of acetylcholine (ACh)-induced endothelium-dependent relaxation. Although N(G)-nitro-L-arginine (L-NNA, 3 x 10(-5) M), an inhibitor of nitric oxide (NO) synthase, significantly inhibited substance P-induced endothelium-dependent relaxation in the presence of indomethacin, about 50% of the vasorelaxant response to substance P remained in the combined presence of L-NNA and indomethacin. By comparison, indomethacin-resistant component of endothelium-dependent relaxation to ACh was mostly suppressed by the treatment with L-NNA plus indomethacin. Substance P-induced non-PGI2, non-NO mediated vascular relaxation was attenuated markedly in high (40 mM) KCl solution or by tetraethylammonium (TEA, 5 x 10(-3) M). Furthermore, substance P-induced non- PGI2, non-NO mediated vascular relaxation was not appreciably affected by glibenclamide (10(-6) M), apamin (10(-7) M), iberiotoxin (1(-7) M), but was greatly attenuated by the combined treatment with charybdotoxin (10(-7) M) plus apamin (10(-7) M), which suggesting that endothelium-derived hyperpolarizing factor(s) (EDHF(s)) mediates the response. Interestingly, after applied repetitively, the substance P-induced vasorelaxant component remaining in the combined presence of indomethacin and L-NNA was decreased more profoundly than the response to substance P in the presence of indomethacin alone. Possible contribution of non-PGI2, non-NO vasorelaxant(s) (EDHF(s)) from the endothelium to the total relaxation response to substance P was greater in thoracic aorta isolated from adult guinea-pigs than that from neonatal ones. These findings suggest that 1) endothelium-dependent vascular relaxation of guinea-pig thoracic aorta in response to substance P is attributable to the release of both NO and EDHF(s); 2) possible release of EDHF(s) from the endothelium of guinea-pig thoracic aorta decreases after repetitive stimulation with substance P; and 3) contribution of EDHF(s) to substance P-induced functional relaxation of the thoracic aorta is greater in adult guinea-pigs than neonatal ones.
authors.affiliation: Department of Pharmacology, Toho University School of Pharmaceutical Sciences, Funabashi-City, Chiba, Japan. yotanaka@phar.toho-u.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Tanaka
authors.forename: H
authors.initials: H
authors.lastname: Kaneko
authors.forename: H
authors.initials: H
authors.lastname: Tanaka
authors.forename: K
authors.initials: K
authors.lastname: Shigenobu
mesh_terms: D000375:Aging / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology; D011464:Epoprostenol / Q000502:physiology; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009569:Nitric Oxide / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology; D026902:Potassium Channel Blockers; D013373:Substance P / Q000494:pharmacology*
chemical_list: D026902:Potassium Channel Blockers; D009569:Nitric Oxide; D013373:Substance P; D011464:Epoprostenol; D009638:Norepinephrine