AJP - Renal Physiology, Vol 250, Issue 4 710-F714, Copyright © 1986 by American Physiological Society
Atrial natriuretic factor can increase renal solute excretion primarily by raising glomerular filtration
M. G. Cogan
Controversy persists on whether atrial natriuretic factor (ANF) raises
renal solute excretion simply by increasing glomerular filtration rate
(GFR) or whether it directly inhibits tubular transport (independent of
changes in flow rate). Free-flow micropuncture techniques were used in 10
Munich-Wistar rats. ANF caused a significant increase in single-nephron and
whole-kidney GFR (41.6 +/- 1.4 to 52.7 +/- 2.3 nl/min and 0.95 +/- 0.05 to
1.24 +/- 0.09 ml/min, respectively). Although absolute proximal sodium,
bicarbonate, and chloride reabsorption increased, the increment in
reabsorption was less than the increase in load; therefore solute delivery
out of the proximal tubule increased by approximately 30-35%. Whole-kidney
electrolyte excretion also rose markedly. When single-nephron and
whole-kidney GFR were reduced back to a control level by aortic
constriction (40.2 +/- 1.8 nl/min and 0.93 +/- 0.05 ml/min, respectively),
proximal transport reverted to normal values despite persistent ANF
administration. Ninety percent of the ANF-induced natriuresis and
chloruresis were simultaneously abolished when GFR was normalized. In
conclusion, ANF has no direct effect on reabsorption in the superficial
proximal convoluted tubule independent of changes in filtration rate.
Although direct effects on more distal or deeper nephron segments are not
precluded, the present data suggest that ANF can increase renal solute
excretion predominantly by acutely augmenting GFR.
