title: Barium and strontium can substitute for calcium in stimulating nitric oxide production in the endothelium of canine coronary arteries.
abstract: We investigated whether Ba2+ and Sr2+ can substitute for Ca2+ in stimulating the nitric oxide (NO) production and cause relaxation in vascular smooth muscle. Ba2+ and Sr2+, like Ca2+, relaxed K(+)-depolarized canine coronary arteries in the presence of diltiazem. The Ba(2+)- and Sr(2+)-induced relaxation was endothelium-dependent and was largely inhibited by NG-monomethyl-L-arginine (L-NMMA) and NG-nitro-L-arginine (L-NNA), but not by indomethacin. These cations increased cyclic GMP levels in the coronary artery to a similar extent, and the increment was completely abolished by L-NMMA. The relaxation induced by each cation was attenuated in the presence of a combination of propranolol, phentolamine and atropine, and L-NNA markedly inhibited any remaining relaxation. This indicates that these cations produce endothelium-dependent relaxation through NO production as well as the relaxation mediated by neurotransmitters. The present study suggests that Ba2+ and Sr2+ can substitute for Ca2+ in the activation of the NO synthase pathway in the endothelium of canine coronary arteries.
mesh_terms: D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001464:Barium / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology; D002413:Cations, Divalent / Q000494:pharmacology; D003331:Coronary Vessels / Q000378:metabolism; D006152:Cyclic GMP / Q000096:biosynthesis; D004285:Dogs; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D007537:Isometric Contraction / Q000187:drug effects / Q000502:physiology; D009126:Muscle Relaxation / Q000187:drug effects; D018377:Neurotransmitter Agents / Q000037:antagonists & inhibitors / Q000502:physiology; D009569:Nitric Oxide / Q000096:biosynthesis* / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000378:metabolism; D019335:Nitroarginine; D011188:Potassium / Q000494:pharmacology; D013324:Strontium / Q000494:pharmacology*; D019323:omega-N-Methylarginine
chemical_list: D002413:Cations, Divalent; D018377:Neurotransmitter Agents; D019335:Nitroarginine; D001464:Barium; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D006152:Cyclic GMP; D011188:Potassium; D002118:Calcium; D007213:Indomethacin; D013324:Strontium