Mechanism of prostaglandin-mediated desensitization to angiotensin II in rabbit aortic rings.

S. JEREZ, PERAL DE BRUNO M. AND COVIELLO A.

Buenos Aires

Congreso; XIII Scientific Meeting of the Inter-American Society of Hypertension.; 1999

Inter-American Society of Hypertension

In previous work we found that endothelium improves tachyphylaxis to angiotensin II (ang II) in isolated rabbit aortic rings. This effect was inhibited by indome athacin (Indo) through a dependent Ca2+ channel mechanism. The purpose of the present work was to study  the role of K+ channels in this effect, using an opener of these channels (cromakalin) and high K+ stimulation. Rabbit aortic rings were mounter to register isometric tension. In one protocol two cumulative doses response curves (CDRC) to ang II separated by 50 min of washing were performed. Cromakalin 10-6 M was added during washing to unrubbed arteries treated or not with Indo 10-5 M. In another protocol unrubbed and rubbed arteries were stimulated with KCl 40mM after which ang II 10-6 M was added to one group. After 50 min washing with normal Krebs or Ca2+ free + EGTA 3mM Krebs, a stimulation with KCl 40 mM was again performed. Cromakalin inhibited the effect of Indo. Response to KCl in rubbed arteries treated with ang II was greater than in unrubbed arteries. This effect was blocked in free Ca2+ medium, without difference  between the controls. These results would indicate that a prostaglandin released from endothelium by ang II increases tachyphylaxis by decreasing acivity of Ca2+ dependent K+ channels.