Electrical nature of sodium transport across the isolated turtle bladder

Abstract

When short-circuited turtle bladders are bathed on both surfaces by sodium-Ringer solutions, the sodium current exceeds short-circuiting current by ca. 44 [mu]a, and one-third to one-half of the nonsodium current is carried by actively transported chloride ion. By inference, the other one-half to two-thirds of nonsodium current is carried by actively transported bicarbonate ion[long dash]an inference based on independently obtained evidence demonstrating active bicarbonate transport across sac preparations. When the transportable anions (chloride and bi-carbonate) are absent or removed from the mucosal surface, the short-circuiting current increases and becomes equal to the net sodium current. The net sodium current in the absence of transportable anions on the mucosal surface is the same as that in the presence of transportable anions. Thus, sodium current is independent of chloride and bicarbonate currents during short-circuiting suggesting that each of the 3 ions move across the bladder through ion selective paths in parallel.