Effect of ouabain on K secretion in cortical collecting tubules from adrenalectomized rabbits.
Previous studies have shown that Na-K-ATPase activity in the cortical collecting tubule of the rabbit increases significantly with mineralocorticoid stimulation and decreases significantly with adrenalectomy. The present study examined the effects of 10(-4) M ouabain on K secretion in the isolated perfused cortical collecting tubules from normal, adrenalectomized, and mineralocorticoid-stimulated animals. Potassium secretion was similar in the tubules from adrenalectomized (3.42 +/- 0.53 pmol X mm-1 X min-1) and from normal rabbits (3.38 +/- 0.36 pmol X mm-1 X min-1). K secretion was greater (15.1 +/- 3.0 pmol X mm-1 X min-1) in tubules from animals receiving 11-deoxycorticosterone acetate (DOCA). Ouabain inhibition of K secretion was 74% for the adrenalectomized group, 86% for the normal group, and 98% for the DOCA-treated group. The degree of inhibition was statistically equivalent among the three groups and not statistically different from complete inhibition of K secretion. Ouabain had no effect on the lumen-positive transepithelial voltage of the cortical collecting tubules from adrenalectomized rabbits but reduced the lumen-negative voltage in tubules from normal rabbits and reversed the polarity of the transepithelial voltage in cortical collecting tubules from DOCA-treated animals. Thus adrenal mineralocorticoids may be necessary for maximal K secretion by the cortical collecting tubule, but they are not essential to maintain K secretion during "normal" K intake. In all groups K secretion is totally dependent on Na-K-ATPase. The lumen-positive transepithelial voltage from DOCA-treated animals after addition of ouabain suggests an additional effect of mineralocorticoid to stimulate secretion of cations (protons) or reabsorption of anions.
D000315:Adrenalectomy; D000450:Aldosterone / Q000097:blood; D000818:Animals; D003900:Desoxycorticosterone / Q000494:pharmacology; D004848:Epithelium / Q000502:physiology; D005260:Female; D066298:In Vitro Techniques; D007672:Kidney Cortex / Q000502:physiology*; D007684:Kidney Tubules / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D010042:Ouabain / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism / Q000652:urine*; D011817:Rabbits
D003900:Desoxycorticosterone; D000450:Aldosterone; D010042:Ouabain; D011188:Potassium