REACTIVITY OF ISOLATED TOAD AORTIC RINGS TO ANGIOTENSION II: THE ROLE OF NITRIC OXIDE

MARAÑON RODRIGO; JOO TURONI CLAUDIO; COVIELLO ALFREDO; PERAL DE BRUNO MARIA

JOURNAL OF COMPARATIVE PHYSIOLOGY B-BIOCHEMICAL SYSTEMIC AND ENVIRONMENTAL PHYSIOLOGY

ELSEVIER

Lugar: USA; Año: 2009 vol. 179 p. 403 - 409

0174-1578

Abstract  Little is known about the vascular actions of angiotensin II (Ang II) and nitric oxide (NO) in Amphibia.This study investigated (1) Ang II contractility, (2) NOconcentrations, and (3) correlations between Ang II contractility, NO concentration and mean arterial pressure (MAP) in isolated Bufo arenarum toad aortic rings.Contractility was measured in isometric conditions, NOconcentrations were determined by the Griess reaction, and MAP was determined by a direct method. In isolated toad aortic rings, Ang II produced a contractile response (292.7 § 89.2 mg; n = 20). Furthermore, a contractile response to norepinephrine (NE) was also obtained. A signiWcant correlation between both the Ang II and NE contractile responses was found (r = 0.89; n = 11; P < 0.01). Administration of Ang II increased MAP values (Basal 16.8 § 1.7; n = 19 vs. Ang II 28.4 § 1.8 mmHg; n = 19; P < 0.001), and the increase of MAP by Ang II was positively correlated with the Ang II contractile response (P < 0.01). Administration of L-NAME also increased MAP values, and this eVect was higher in those toads that presented a lower pressure response to Ang II (Pearson r = ¡0.68; P < 0.05). NO was present in all aortic rings, and its concentrations were negatively related to the Ang II contractile response (P < 0.036) and pressure response (Pearson r = ¡7.08; P < 0.001). These Wndings suggest that, in the B. arenarum toad, the NO system contra-regulates both the contractile and pressure Ang II responses, although its action could be different in each specimen.