Cardiovascular and renal nitric oxide synthase activity and atrial natriuretic peptide in spontaneous hypertensive rats.

COSTA MARÍA DE LOS ÁNGELES; ELESGARAY ROSANA; CANIFFI CAROLINA; LENCINAS GISELA; BALASZCZUK ANA MARÍA; ARRANZ CRISTINA

Milán

Congreso; Fifteenth European Meeting on Hypertension.; 2005

European Society of Hypertension.

Objective: In previous studies we demonstrated that NO-system activation would be one of the mechanisms involved in ANP vascular, cardiac and renal actions in Wistar rats. NPR-C natriuretic receptor would mediate the activation of nitric oxide synthase (NOS) by ANP in cardiac atria. In kidney and artery, NOS activation would also involve NPR-A and/or B natriuretic receptors. The aim of the present study was to investigate the effects of ANP on vascular, cardiac and renal NOS activity in spontaneous hypertensive rats (SHR). Design and Method: SHR and Wistar Kyoto rats (WKY) were sacrificed and NOS catalytic activity was determined in renal medulla and cortex, aorta artery and cardiac atria by measuring the conversion of L-[U14C]-arginine to L-[U14C]-citrulline, in presence of ANP or cANP (4-23), a selective NPR-C ligand. Results: The results are expressed as percentage of increase respect to the basal activity of NOS.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            ANP (1 µM)                        cANP (4-23) (1 µM)                                        WKY                  SHR                WKY                  SHR                                       (%)                  (%)                   (%)                   (%)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       Cortex                  44.1±5.2          30.0±4.7*         20.9±4.6*          19.8±3.5#  Medulla                 35.5±3.3          26.6±5.7*         21.5±3.1*          18.3±4.0#  Aorta artery         76.5±15.5         40.3±9.3*         24.5±5.7*          23.1±5.5#  Atria                     55.3±7.2          53.4±9.8          52.9±10.9         49±10.5                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   *p < 0.01 vs WKY with ANP; # p < 0.01 vs SHR with ANP.             Conclusions: ANP and cANP (4-23) increased NOS activity in all studied tissues of both groups. In kidney and artery, the increase in NOS activity induced by ANP was lower in SHR compared with WKY. The activation of NOS induced by cANP (4-23) was similar in both groups. In atria, where ANP activate NOS via NPR-C interaction, the increase in NOS activity showed no changes in SHR and WKY. Otherwise, in kidney and artery, where NPR-A and/or B are also involved, the increase induced by ANP was lower in SHR than WKY. Results: These results would indicate that SHR could present an alteration in NPR-A/B and/or in particulate guanylate cyclase.