Calcium-induced vasodilation due to increase in nitric oxide formation in the vascular bed of rabbit ear preparation.
Participation of calcium-induced vasodilation (due to an increase in synthesized nitric oxide (NO) content in endothelial cells) in the arterio-venous circulation, including the vascular bed was investigated by the vessel perfusion method in the isolated rabbit ear preparation. The perfusion medium used was a tris-buffered solution. When CaCl2 (6.25, 12.5 and 25 mg) was injected in the perfused vessel of the rabbit ear preparation, dose-dependent vasocontraction was observed when vascular tone was kept at a normal level. However, CaCl2 dose-dependently induced vasodilation of the vessel when it was continuously contracted by norepinephrine (1.2 x 10(-7) M). This calcium-induced vasodilation was inhibited in the presence of NG-nitro-L-arginine (5 x 10(-5) M), a selective inhibitor of NO synthesis, and methylene blue, a guanylate cyclase inhibitor, although it was rarely affected by indomethacin (10(-5) M), a cyclooxygenase inhibitor. Calcium-induced vasodilation was also obtained in the in situ circulation containing vascular bed, and this suggests that the vasodilation was due to a Ca(2+)-induced increase in the synthesis of NO derived from endothelial cells.
Takasugi
N
N
Department of Pharmacology, Hiroshima University School of Medicine, Japan.
D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D002122:Calcium Chloride / Q000494:pharmacology*; D004431:Ear, External / Q000098:blood supply; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008751:Methylene Blue / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D019335:Nitroarginine; D011817:Rabbits; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology
D019335:Nitroarginine; D009569:Nitric Oxide; D001120:Arginine; D007545:Isoproterenol; D002122:Calcium Chloride; D008751:Methylene Blue; D007213:Indomethacin