AJP - Renal Physiology, Vol 251, Issue 2 220-F225, Copyright © 1986 by American Physiological Society
Effect of synthetic ANP on renal and loop of Henle functions in the young rat
D. R. Roy
The present studies were undertaken to determine, by recollection
micropuncture, the effect of a synthetic atrial natriuretic peptide (ANP)
on the absolute and fractional deliveries of water and sodium to the
juxtamedullary end-descending limb. Two groups of young female
Munich-Wistar rats were studied: control (n = 8) received the vehicle only;
and ANP (n = 12) received a prime followed by the constant infusion of a
synthetic rat atrial peptide (28 amino acids). With the infusion of ANP,
clearance of p-[14C]aminohippurate [( 14C]PAH) and glomerular filtration
rate (GFR) fell significantly. Despite this fall in GFR and renal plasma
flow, ANP produced a 2-fold increase in urine volume and a 10-fold increase
in sodium excretion. Absolute and fractional sodium deliveries to the
end-descending limb increased by approximately 30% in the ANP group,
whereas mean juxtamedullary single-nephron glomerular filtration rate
(SNGFR) remained stable. In three additional rats prepared for
micropuncture of the superficial end-accessible proximal tubule, ANP
reduced cortical SNGFR by approximately 15%. By contrast, GFR did not
decline in response to ANP in larger rats, when treated identically. We
conclude that in young rats ANP can produce a natriuresis in the absence of
a rise in GFR; the fall in GFR observed following ANP is due presumably to
the immaturity of the animals used in these studies; and ANP produces a
rise in absolute and fractional water and sodium deliveries to the
end-descending limb that cannot be attributed to a change in
SNGFR.(ABSTRACT TRUNCATED AT 250 WORDS)
