The effect of acute saline volume expansion on renal Na-K-ATPase.
To examine the role of Na-K-ATPase in the natriuresis that occurs after acute extracellular volume expansion, we performed acute clearance experiments and in vitro analysis of renal microsomal ATPase activity in rats receiving intravenous 0.9% sodium chloride (0.1 ml/100 g bw/min). Despite increased absolute reabsorption of filtered sodium (196 +/- 8.1 vs. 165 +/- 11.4 uEq/min, p less than 0.05), renal medullary microsomal Na-K-ATPase activity was decreased from 134 +/- 5.9 to 110 +/- 6.3 pmol Pi/mg protein/hour (p less than 0.02). No changes occurred in cortical or papillary regions and Mg-ATPase was unaffected. Similar results were obtained after adding 4 mEq/l potassium chloride to the infusion to prevent any fall in serum K+. These data suggest that a considerable percentage of sodium reabsorption is suppressed in acutely volume expanded animals and it is proposed that this is mediated by inhibition of medullary Na-K-ATPase.
D000818:Animals; D001693:Biological Transport, Active; D002463:Cell Membrane Permeability; D005110:Extracellular Space / Q000502:physiology; D005440:Fluid Therapy; D007668:Kidney / Q000201:enzymology* / Q000502:physiology; D008297:Male; D008861:Microsomes / Q000201:enzymology; D009318:Natriuresis; D051381:Rats; D012462:Saline Solution, Hypertonic; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism* / Q000502:physiology
D012462:Saline Solution, Hypertonic; D000254:Sodium-Potassium-Exchanging ATPase