Some aspects of proximal tubular sodium chloride reabsorption in Necturus kidney

Whittembury, Guillermo; Diezi, Françoise; Diezi, Jacques; Spring, Kenneth; Giebisch, Gerhard
January 1975
Kidney International;Jan1975, Vol. 7 Issue 1, p293
Academic Journal
Renal tubular reabsorption of fluid and sodium was measured by clearance methods in the doubly perfused Necturus kidney in which the bicarbonate concentration was varied between 0 and 60 mEq/liter. The effects of Diamox (2.2 × 10-3M), ouabain (10-5M) and ethacrynic acid (10-4M) and of acidosis were also investigated. in addition to clearance experiments, stationary microperfusion experiments were carried out on proximal tubules to measure volume flow and steady-state sodium and chloride concentration differences across the tubular epithelium. In some experiments, the transepithelial electrical potential difference was also measured using an axial electrode system. The following results were obtained: 1) Bicarbonate is not essential to the operation of renal tubular fluid and sodium transport. 2) Total renal and proximal tubular fluid and sodium transport are partially inhibited by Diamox, ouabain and ethacrynic acid. 3) The proximal tubule maintains a significant transepithelial sodium and chloride concentration difference and a significant electrical potential difference (lumen-negative) in the presence of a poorly permeant nonelectrolyte. The direction and magnitude of the electrical polarization fully accounts for the observed chloride concentration difference. The data support the thesis that sodium chloride transport across the proximal tubular epithelium takes place by active sodium transport and electrically coupled passive chloride reabsorption. Important species differences with respect to mammalian transport mechanisms are discussed.


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