Mineralocorticoid effect on K+ permeability of the rabbit cortical collecting tubule.
Mineralocorticoid hormones stimulate Na+ absorption and K+ secretion by the cortical collecting tubule. There is good evidence that this stimulation involves increasing luminal membrane Na+ permeability and the turnover rate (or number) of the Na+-K+ pumps. These experiments were designed to examine whether mineralocorticoid hormones also increase cell K+ permeability. Using 42K tracer measurements in tubules treated with amiloride to inhibit active Na+ and K+ transport, passive K+ permeation increased with increasing mineralocorticoid effect. Net Na+ absorption and the (passive) K+ efflux rate coefficient (KK) showed a linear relationship. The stimulatory effect was evident in vitro since 0.2 microM aldosterone added to the bath of tubules harvested from NaCl-loaded rabbits increased KK at 3 hrs while time controls showed no change. Since these tubules were also treated with amiloride, this increase in KK was not dependent on increasing Na+ absorption. The results indicate that in addition to the well-described effects of aldosterone on Na+ permeability and cell metabolism, the mineralcorticoid effect includes an increase in cellular K+ permeability.
D000450:Aldosterone / Q000494:pharmacology*; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001693:Biological Transport, Active / Q000187:drug effects; D003900:Desoxycorticosterone / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D007684:Kidney Tubules / Q000502:physiology*; D007685:Kidney Tubules, Collecting / Q000502:physiology*; D010042:Ouabain / Q000494:pharmacology; D010539:Permeability; D011188:Potassium / Q000502:physiology*; D011817:Rabbits; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors
D003900:Desoxycorticosterone; D000450:Aldosterone; D010042:Ouabain; D000584:Amiloride; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium