RESUMEN
We studied the kinetics of HCO-3 reabsorption in the middle proximal (MPT) and distal convoluted tubules (DCT) by measuring continuously intratubular pH with Sb-microelectrodes in stopped-flow microperfusion (HCO-3, 30 mM Ringer) experiments. Male Wistar rats (240-280 g) were injected ip with LiCl (4mEqkg-1 day-1) for 4 days (Li) and were compared to controls (C). Steady-state pH increased in MPT from 6.64 + or - 0.02(57) to 6.89 + or - 0.02(45), mean + or - SEM (number of measurements) on tissue from 13 rats in each group, and from 6.87 + or - 0.5(30) to 7.08 + or - 0.01(63) in DCT. HCO-3 reabsorption decreased from 1.32 + or - 0.08(57) to 0.96 + or - 0.4(45) nmol cm-2 s-1 in MPT and from 0.85 + or - 0.07(30) to 0.45 + or - 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