[Atrial natriuretic factor. Systemic and regional hemodynamic profile and interaction with the alpha-adrenergic system in pithed SHR rats].

The hemodynamic effects of ANF (1 and 5 micrograms/kg/min) and its potential interactions with the sympathetic system were investigated at the systemic and regional (pulsed Doppler) levels in the pithed SHR. ANF dose-dependently decreased cardiac output CO, renal (RBF), mesenteric (MBF) and hindquarter (HQBF) blood flows and increased the corresponding vascular resistances: total peripheral (TPR), renal (RR), mesenteric (MR) and hindquarter (HQR), all these effects being significant at 5 micrograms/kg/min. Mean blood pressure (MBP) and heart rate were also significantly decreased at 5 micrograms/kg/min. ANF significantly reduced the responses to cirazoline of MBP, TPR and RR (1 microgram/kg/min) and of MR (5 micrograms/kg/min) but did not affect those of HQR ANF also significantly reduced the responses to UK-14,304 of MBP, TPR and MR (5 micrograms/kg/min) but did not affect those of RR and HQR. These data indicate that (a) ANF, in the absence of reflex phenomenons, exerts intrinsic regional vasoconstrictor effects, (b) ANF exhibits a postsynaptic sympatho-inhibitory effect. The latter is more marked vs the alpha 1-(especially renal) than vs the alpha 2-adrenoceptor-mediated responses but does not affect the hindquarter vascular bed, which suggest that its contribution to the overall antihypertensive action of ANF is of limited importance.