Effects of vanadate on vascular contractility and membrane potential in the rabbit aorta.
Isolated rabbit aortic ring with intact endothelial cell preparations precontracted with NE (10(-7) M) were relaxed by vanadate in a dose dependent manner (from 0.2 to 2 mM). Application of vanadate and ACh during the tonic phase of high K+(100 mM)-induced contraction showed a slight relaxation in contrast to that in NE-induced contraction, but sodium nitroprusside (10 microM) more effectively relaxed the aortic ring preparations in high K+ contraction than that of vanadate. Vanadate-induced relaxation in NE-contracted aortic rings was reversed by application of BaCl2 (50 microM) or glibenclamide (10 microM). Furthermore, Vanadate hyperpolarized membrane potential of smooth muscle cells in endothelium-intact aortic strips and this effect was abolished by application of glibenclamide. The above results suggest that vanadate release EDHF (Endothelium-Derived Hyperpolarizing Factor), in addition to EDRF (Endothelium-Derived Relaxing Factor) from endothelial cell. This EDHF hyperpolarize the smooth muscle cell membrane potential via opening of the ATP-sensitive K+ channel and close a voltage dependent Ca++ channel. So it is suggested that the vanadate-induced relaxation of rabbit thoracic aortic rings may be due to the combined effects of EDRF and EDHF.
Chung
S M
SM
Department of Physiology, Yonsei University College of Medicine, Seoul, Korea.
Ahn
D S
DS
Seok
H S
HS
Jeong
Y
Y
Kang
B S
BS
D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D011188:Potassium / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology; D011817:Rabbits; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology*; D014664:Vasodilation / Q000187:drug effects*
D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D014638:Vanadates; D011188:Potassium