The present study evaluates the interrelationship between the alteration in atrial natriuretic factor (ANF) and the renal handling of Na in rats with chronic aortocaval (a-v) fistula, an experimental model of congestive heart failure. Balance studies in these animals showed two distinct patterns of Na excretion: some rats developed progressive Na retention [urinary sodium excretion (U(Na)V)<100 μeq/24 h], whereas others compensated and returned to normal Na balance (U(Na)V>1,200 μeq/24 h). Base-line plasma ANF levels were equally elevated in Na-retaining and compensated rats with a-y fistula (588 ± 70 vs. 621 ± 114 pg/ml, P, NS). However, the response of the two groups to exogenous administration of synthetic rat ANF-(101-126) in incremental doses varied greatly. ANF infusion increased the fractional Na excretion (FE(Na)) in compensated animals from 0.12 ± 9.93 to 2.6 ± 0.5%, whereas the rise in FE(Na) in Na-retaining animals was markedly blunted (0.11 ± 0.06 to 0.89 ± 0.35%). A similar pattern of ANF action was observed on the glomerular filtration rate and urine flow. The blunted response to ANF in the Na-retaining animals was associated with a marked increase in plasma renin activity (PRA) (35.6 ± 6.9 vs. 4.5 ± 0.7 ng ANG I·ml-1·h-1 in sham control rats, P < 0.05) and plasma aldosterone levels (729.3 ± 28.2 vs. 42.6 ± 18.4 ng/dl in sham control rats, P < 0.05). In contrast, PRA (6.7 ± 1.1 ng ANG I·ml-1·h-1) and plasma aldosterone (34.2 ± 8.2 ng/dl) in the compensated animals did not differ from the sham control rats. Finally, chronic inhibition of converting enzyme (with enalapril) in Na-retaining rats resulted in a significant natriuresis. The data suggest that the balance between the two opposing hormonal systems, ANF and the renin-angiotensin system, is an important determinant of Na excretion in this model of heart failure and that removal of the influence of the renin-angiotensin system facilitates the expression of the natriuretic effect of ANF.
|Original language||English (US)|
|Journal||American Journal of Physiology - Regulatory Integrative and Comparative Physiology|
|State||Published - 1988|
ASJC Scopus subject areas
- Physiology (medical)