Effects of potassium depletion on renal tubular chloride transport in the rat.

Potassium depletion (KD) causes renal chloride-wasting. To investigate the effects of KD on renal tubular reabsorption of chloride, balance, clearance, micropuncture, and microinjection studies were performed on potassium-depleted rats. KD was produced by omitting potassium from the diet and by administration of DOCA on days 2 and 3; rats were studied on days 9 to 12. Diets were chloride-free in both control and KD groups. In the KD group, balance experiments confirmed greater chloride depletion and continued chloride-wasting, and clearance studies showed an increased FECl. Muscle potassium was reduced by 27% as compared to control. Whole kidney and single nephron GFR were reduced in KD rats to 72 and 74% of control. Fractional (6 +/- 6% vs. 22 +/- 4%, P less than 0.05) and absolute chloride reabsorption in the proximal tubule was not different. Fractional reabsorption of delivered chloride was reduced in the loop of Henle (92 +/- 0.8% in KD vs. 95 +/- 0.7% in control, P less than 0.02). Transtubular chloride ratio (0.28 +/- 0.02 vs. 0.21 +/- 0.02, P less than 0.02) was increased at the early distal tubule. Fractional delivery of chloride (8 +/- 0.9 vs. 5 +/- 0.5%, P less than 0.02), and fluid (26 +/- 1 vs. 22 +/- 1%, P less than 0.05) were also increased in KD at the early distal tubule. Recovery of chloride 36 injected into late distal tubules was 88 +/- 1% on a normal chloride intake, 62 +/- 2% in chloride depletion, and 88 +/- 2% in potassium and chloride depletion. Thus, KD depresses chloride reabsorption in the proximal tubule and in the loop of Henle, and it decreases chloride 36 efflux from the collecting duct.