Impairment of the renal tubular acidification kinetics by lithium

We studied the kinetics of HCO3- reabsorption in the middle proximal (MPT) and distal convoluted tubules (DCT) by measuring continuously intratubular pH with Sb-microelectrodes in stopped-flow microperfusion (HCO3-, 30 mM Ringer) experiments. Male Wistar rats (240-280 g) were injected ip with LiCl (4 mEq kg-1 day-1) for 4 days (Li) and were compared to controls (C). Steady-state pH increased in MPT from 6.64 +/- 0.02 (57) to 6.89 +/- 0.02 (45), mean +/- SEM (number of measurements) on tissue from 13 rats in each group, and from 6.87 +/- 0.05 (30) to 7.08 +/- 0.01 (63) in DCT. HCO3- reabsorption decreased from 1.32 +/- 0.08 (57) to 0.96 +/- 0.04 (45) nmol cm-2 s-1 in MPT and from 0.85 +/- 0.07 (30) to 0.45 +/- 0.04 (63) in DCT. These data indicate that lithium affected the acidification mechanism in MPT and DCT, probably through an impairment of the Na(+)-H+ antiport in both tubular segments.