Characterization of synthetic atrial natriuretic factor: vasodilator profile and decreased vascular sensitivity in hypertensive rats.

Synthetic atrial natriuretic factor (ANF) relaxed agonist-induced tone in rabbit aortic rings as well as intrinsic, myogenic contractions in the isolated rabbit facial vein (IC50s = 0.1 to 5 nM). Tissues depolarized by high levels of K+ were refractory to ANF. A similar profile was obtained with extracts of rat atria and with sodium nitroprusside (NaNP) but not other vasodilators. Aortas from spontaneously hypertensive rats (SHR) were significantly less sensitive to the relaxant effects of ANF (and NaNP) than were aortas from Wistar-Kyoto (WKY) rats. However, atrial extracts from SHR were more effective than WKY rat atrial extracts in relaxing normotensive aortic rings. Radioimmunoassay analysis confirmed a small increase in ANF immunoreactive material in SHR compared with WKY rat atria. The similar vascular profile for both ANF and NaNP suggests that these agents share a common mechanism of action. A reduced end organ responsiveness in SHR may lead to an increased atrial content of ANF in these animals.