Water depletion, not oral sodium loading, increases levels of sodium, potassium-dependent adenosine triphosphatase inhibitors in rat plasma.
In order to define a physiological role for circulating inhibitors of sodium, potassium-dependent adenosine triphosphatase (Na+,K+-ATPase), plasma was obtained from control, water deplete, water repleted, sodium deplete and sodium loaded rats. The effect of this plasma on Na+,K+-ATPase activity, and its transport equivalent 86Rb uptake, was measured in separated guinea pig renal cortical tubules. Plasma from water deplete rats had a raised plasma osmolality and sodium concentration and a significant inhibitory effect on Na+,K+-ATPase (14%) and 86Rb uptake (24%) compared with control or water repleted rats. Inhibition of Na+,K+-ATPase and 86Rb transport was not seen with plasma from rats after dietary sodium loading (urine sodium 5.2 +/- 0.9 mmol/day) compared with low sodium diet controls (urine sodium 0.41 +/- 0.08 mmol/day). Des-amino arginine vasopressin in vivo produced no inhibition of Na+,K+-ATPase or Rb transport. These studies suggest, that in terms of common homoeostatic insults, circulating inhibitors of Na+,K+-ATPase are more responsive to water depletion than to oral sodium loading. The inhibitors may fulfil a physiological role in increasing sodium excretion to maintain osmolality after dehydration.
D000818:Animals; D001693:Biological Transport, Active; D006168:Guinea Pigs; D007684:Kidney Tubules / Q000378:metabolism; D009994:Osmolar Concentration; D011188:Potassium / Q000097:blood; D051381:Rats; D011919:Rats, Inbred Strains; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000097:blood / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*; D014868:Water Deprivation
D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium; D011188:Potassium