title: Effect of synthetic ANP on renal and loop of Henle functions in the young rat.
abstract: 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)
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D004231:Diuresis / Q000187:drug effects; D005260:Female; D005919:Glomerular Filtration Rate; D007668:Kidney / Q000187:drug effects*; D007677:Kidney Function Tests; D007684:Kidney Tubules / Q000187:drug effects*; D008138:Loop of Henle / Q000187:drug effects*; D009399:Nephrons / Q000378:metabolism; D051381:Rats; D012964:Sodium / Q000652:urine
chemical_list: D009320:Atrial Natriuretic Factor; D012964:Sodium