AJP - Renal Physiology, Vol 258, Issue 5 1388-F1393, Copyright © 1990 by American Physiological Society

ARTICLES

Active and passive chloride transport by the rabbit cortical collecting duct

C. S. Wingo
Department of Medicine, College of Medicine, University of Florida, Gainesville.

Dietary K intake has been shown to influence solute flux in the cortical collecting duct (CCD). We recently observed active Cl secretion by the CCD when rabbits were fed a K-rich diet. The present studies examined two different methods of K loading (KHCO3 or KCl) on net Cl flux (JNet Cl), active Cl flux (JA Cl), and passive Cl flux (JP Cl) by the rabbit CCD. These two methods of K loading were compared with a low-K diet (control or NaHCO3 diet) that had the same anion composition as the KHCO3 diet (Na for K substitution). In the low-K group there was neither significant net Cl transport nor active Cl secretion. Increasing dietary K content (KHCO3 group) resulted in significant net Cl secretion (JNet Cl = -26.3 +/- 9.3 pmol.mm-1.min-1). Moreover, K secretion was significantly greater (23.8 +/- 4.3 pmol.mm-1.min-1) and transepithelial voltage (VT) was more lumen negative (-14.8 +/- 5.9 mV) compared with the low-K group (P less than 0.05). Consequently, there was both significant passive Cl absorption and significant active Cl secretion. In the KCl group there was significant net Cl absorption (JNet Cl = 17.2 +/- 5.1 pmol.mm-1.min-1, P less than 0.05 vs. low-K diet). However, Na absorption significantly exceeded JNet Cl (JNet Na = 42.0 +/- 7.2 pmol.mm-1.min-1, P less than 0.01), and this group also exhibited the most lumen-negative voltage (VT = -35.4 +/- 5.4 mV).(ABSTRACT TRUNCATED AT 250 WORDS)

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