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.
MacLaughlin
M
M
Departamento de Fisiologia e Biofísica, Instituto de Ciências Biomédicas, Universidade de São Paulo, Brasil.
Mello-Aires
M
M
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000378:metabolism; D008094:Lithium / Q000009:adverse effects*; D008297:Male; D011677:Punctures; D051381:Rats; D011919:Rats, Inbred Strains
D001639:Bicarbonates; D008094:Lithium