Effects of ouabain and amiloride on Na pathways in turtle bladders.
In a Na-rich bathing system, addition of amiloride to the mucosal fluid of turtle bladders produces decreased in the transepithelial potential difference (PD), short-circuiting current (I-sc), and conductance. Removal of amiloride results in complete reversal of these changes; and this reversibility is incomplete in amiloride-blocked bladders exposed to ouabain. In a Na-free bathing system, step increased in mucosal [Na] evoke rapid initial spikes in PD, Isc, and conductance, the magnitudes of which are independent of prior ouabain treatment. After these spikes, PD and Isc in the ouabain-treated bladder rapidly decay, while conductance remains unchanged and high. This unchanging conductance, plus the fact that ouabain inhibits half the microsomal (Na plus K). ATPase of this tissue within 1 min, suggests that ouabain inhibits Na pumping without changing tissue conductance. The delayed decrease in conductance (beginning 30 min after ouabain addition), a nonspecific and secondary effect of ouabain, is due to a concomitant collapse of the intercellular channels.
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002463:Cell Membrane Permeability / Q000187:drug effects; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D008861:Microsomes / Q000201:enzymology; D010042:Ouabain / Q000494:pharmacology*; D011719:Pyrazines / Q000494:pharmacology*; D012964:Sodium / Q000378:metabolism*; D013997:Time Factors; D014426:Turtles; D001743:Urinary Bladder / Q000378:metabolism*
D011719:Pyrazines; D010042:Ouabain; D000584:Amiloride; D012964:Sodium; D000251:Adenosine Triphosphatases