Reactivity of isolated toad aortic rings to angiotension II: the role of nitric oxide

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

JOURNAL OF COMPARATIVE PHYSIOLOGY B-BIOCHEMICAL SYSTEMIC AND ENVIRONMENTAL PHYSIOLOGY

Springer Berlin / Heidelberg

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

0174-1578

Little is known about the vascular actions ofangiotensin II (Ang II) and nitric oxide (NO) in Amphibia.This study investigated (1) Ang II contractility, (2) NOconcentrations, and (3) correlations between Ang IIcontractility, 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, andMAP was determined by a direct method. In isolated toadaortic rings, Ang II produced a contractile response(292.7 § 89.2 mg; n = 20). Furthermore, a contractileresponse to norepinephrine (NE) was also obtained. A signiWcantcorrelation between both the Ang II and NE contractileresponses was found (r = 0.89; n = 11; P < 0.01).Administration of Ang II increased MAP values (Basal16.8 § 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 positivelycorrelated with the Ang II contractile response(P < 0.01). Administration of L-NAME also increasedMAP values, and this eVect was higher in those toads thatpresented a lower pressure response to Ang II (Pearsonr = ¡0.68; P < 0.05). NO was present in all aortic rings,and its concentrations were negatively related to the Ang IIcontractile response (P < 0.036) and pressure response (Pearson r = ¡7.08; P < 0.001). These Wndings suggestthat, in the B. arenarum toad, the NO system contra-regulatesboth the contractile and pressure Ang II responses,although its action could be diVerent in each specimen.