Effects of amiloride in the medullary collecting duct of rat kidney.
The in vivo microcatheterization technique was used to study amiloride-induced transport alterations in the inner medullary collecting duct. Amiloride treated rats (0.1 mg/hr) had significant diuresis and natriuresis, as well as antikaliuresis, compared to untreated controls. The relative decrease in potassium excretion was associated with a significant rise in plasma potassium concentration. Net sodium transport in the duct was decreased from 83 + 3 to 46 + 6 per cent of delivered load, as a result of amiloride treatment. Smaller, but statistically significant, reductions (P less than 0.01) were seen for fluid and chloride reabsorptions (from 66 + 3 to 51 + 4%, and from 72 + 4 to 52 + 5%, respectively). Potassium reabsorption increased from 15 + 8 to 61 + 6% of delivered load. The data indicated that amiloride natriuresis is determined primarily by inhibition of sodium reabsorption in the medullary collecting duct, probably due to blockade of a specific Na channel. The antikaliuresis, on the other hand, appears to be due to inhibition of secretion both in upstream nephron segments and in the duct itself.
D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D001693:Biological Transport, Active; D002712:Chlorides / Q000097:blood; D004231:Diuresis / Q000187:drug effects; D007684:Kidney Tubules / Q000187:drug effects*; D007685:Kidney Tubules, Collecting / Q000187:drug effects*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000097:blood
D002712:Chlorides; D000584:Amiloride; D012964:Sodium