Atrial natriuretic factor and changes in the aldosterone response to angiotensin II in sodium depleted dogs.

The effects of physiological shifts in plasma atrial natriuretic factor (ANF) concentrations on angiotensin II/aldosterone relationships during changes in sodium status were assessed in 6 conscious beagle dogs. Incremental infusions of angiotensin II (3, 9 and 27ng/kg/min) were administered on three occasions. The animals were studied in sodium replete and deplete states and on a third occasion, again while sodium deplete, with a background constant low-dose infusion of ANF (1.5pmol/kg/min) sufficient to enhance the low endogenous plasma ANF values observed in sodium depletion to match those observed in the sodium replete state. Sodium depletion caused a leftward shift and steepened the slope of the relationship between achieved arterial angiotensin II concentrations and the plasma aldosterone response. This effect was significantly attenuated (approximately 50%) by the low dose ANF infusions which tended to flatten the slope of the angiotensin II/aldosterone curve (ns) and shifted it significantly to the right (p < 0.05). These data suggest subtle shifts in endogenous levels of plasma ANF, accompanying changes in sodium status, are a major contributor to the associated alterations in angiotensin II/aldosterone relationships. Low dose ANF also significantly reduced the effect of angiotensin II on arterial pressures but did not alter natriuresis.