Relationship between dietary Na+ intake, aldosterone and colonic amiloride-sensitive Na+ transport.
The effect of changes in dietary Na+ intake on plasma aldosterone levels and electrogenic amiloride-sensitive Na+ transport (Iamil) was studied in the rat distal colon. Five groups of rats were fed on diets containing different amounts of Na+. Estimated Na+ intake ranged from about 400-80,000 mu equiv Na+/kg body weight (BW) per d. Both variables investigated, Iamil and plasma aldosterone, depended non-linearly on Na+ intake. Reduction of the daily Na+ intake increased plasma aldosterone levels and if these levels reached the value 200 pg/ml or more then Iamil was induced. The corresponding Na+ intake was 1300 mu equiv Na+/kg BW per d. Iamil was not observed at lower aldosterone levels and higher Na+ intakes. Aldosterone infusion for 7 d produced similar changes in Iamil compared with dietary Na(+)-depleted animals and made the estimation of maximum transport capacity of Iamil possible. We conclude that Iamil operates only if Na+ intake decreases below minimal Na+ requirement in growing rats and that the maximum transport capacity of this pathway is reached only after very severe Na+ deprivation.
Pácha
J
J
Institute of Physiology, Czech Academy of Sciences, Prague.
Pohlová
I
I
D000450:Aldosterone / Q000097:blood* / Q000494:pharmacology; D000584:Amiloride / Q000378:metabolism*; D000818:Animals; D002712:Chlorides / Q000378:metabolism; D003106:Colon / Q000378:metabolism*; D017136:Ion Transport; D008297:Male; D009994:Osmolar Concentration; D011188:Potassium / Q000378:metabolism; D017419:Potassium, Dietary / Q000008:administration & dosage; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism*; D012982:Sodium, Dietary / Q000008:administration & dosage*
D002712:Chlorides; D017419:Potassium, Dietary; D012982:Sodium, Dietary; D000450:Aldosterone; D000584:Amiloride; D012964:Sodium; D011188:Potassium