Effect of synthetic ANP on renal and loop of Henle functions in the young rat
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: 1) control received the vehicle only; and 2) ANP 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-( UC)aminohippurate (( UC(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 approx.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 approx.15%. By contrast, GFR did not decline in response to ANP in larger rats, when treated identically. The authors conclude that 1) in young rats ANP can produce a natriuresis in the absence of a rise in GFR; 2) the fall in GFR observed following ANP is due presumably to the immaturity of the animals used in these studies; and 3) 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. The relatively small rise in fractional sodium delivery to the end-descending limb, most probably due to inhibition of sodium and water reabsorption in the juxtamedullary proximal tubule and/or thin descending limb, accounts for only a smallproportion of sodium excretion in the final urine.
- Research Organization:
- McGill Univ., Montreal, Quebec
- OSTI ID:
- 6281159
- Journal Information:
- Am. J. Physiol.; (United States), Vol. 251:2
- Country of Publication:
- United States
- Language:
- English
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