Enhanced natriuretic response to intrarenal infusion of atrial
natriuretic factor during ovine pregnancy.
Fan, L., S. Mukaddam-Daher, J. Gutkowska, B. S. Nuwayhid, E. W.
Quillen, Jr.
Department of Obstetrics and Gynecology, McGill University,
Montreal, Quebec H3A 1A1 and Centre de Recherche Hotel-Dieu de
Montr[acute]eal, Montreal
APStracts 2:0341R, 1995.
Volume loading and intravenous infusion studies have suggested that
the natriuretic response of atrial natriuretic factor (ANF) is
blunted or unaltered during pregnancy, but these findings may be
influenced by changes in peripheral metabolism or clearance. To
better define the direct renal actions of ANF, three doses (0.3, 1.5
and 3.0 pmol x kg 1 x min 1) of ANF were infused directly into the
renal artery of nonpregnant (n=7) and 115-135 day pregnant (n=6)
unilaterally nephrectomized conscious sheep. Each dose was
administered on a separate day according to a protocol that consisted
of two 20 min control, two 20 min ANF infusion, and three 30 min
recovery periods. The levels of basal mean arterial pressure averaged
86 +/- 5 mmHg, and were similar and constant throughout all protocols
in nonpregnant and pregnant ewes. Glomerular filtration rate (GFR)
and renal blood flow (RBF) were increased during pregnancy; but GFR,
RBF, and fractional proximal tubular reabsorption were not
significantly altered by infusion of ANF. Nonpregnant sheep exhibited
a selective renal response that was limited to an increase in UNaV.
Pregnant sheep exhibited a selective renal response that included
increases in UNaV and UFR produced by suppression of distal sodium,
and presumably, fluid reabsorption. The natriuretic and diuretic
response of pregnant sheep was much greater than that of nonpregnant
sheep despite a smaller proportional increment in intrarenal ANF
concentration. These data suggest that the ovine renal response to
ANF is limited to actions on the distal tubule that are enhanced
during pregnancy.
Received 27 March 1995; accepted in final form 29 November 1995.
APS Manuscript Number R205-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 12 December 95