Mechanisms of K⁺ Transport in Isolated Turtle Urinary Bladder: INDUCTION OF ACTIVE K⁺ SECRETION IN A K⁺-ABSORBING EPITHELIUM

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Abstract

Transepithelial K+ movement was studied in vitro in the short-circuited turtle bladder by increasing luminal K+ permeability and by inhibiting the basolateral Na/K pump. Luminal addition of amphotericin B caused net K+ secretion (180±52 nmol/h) compared with net K+ absorption (42±6 nmol/h) in control bladders. Serosal ouabain and luminal amiloride abolished K+ secretion in amphotericin-treated bladders; ouabain restored net absorption (45±16 nmol/h). The direction and rate of net K+ transport are controlled by the relative K+ permeabilities and the Na/K pump sites at the two cell membranes of the epithelium.

Authors

Russell F. Husted, Philip R. Steinmetz