Effect of bafilomycin on proximal bicarbonate absorption in the rat.
To evaluate the relative importance of the V-type H(+)-ATPase in proximal bicarbonate reabsorption in vivo, proximal tubules of male and female Wistar rats (180 to 260 g) were perfused with bicarbonate-Ringer solution with and without the addition of 2 microM bafilomycin A1. Bafilomycin significantly increased stationary pH from 6.75 +/- 0.05 (N = 39) to 6.86 +/- 0.03 (N = 82), the stationary concentration of bicarbonate from 5.24 +/- 0.62 to 6.33 +/- 0.46 mM and the half-time of acidification from 3.72 +/- 0.22 to 4.65 +/- 0.25 s, and significantly decreased net bicarbonate reabsorption from 3.17 +/- 0.21 to 2.55 +/- 0.15 nmol s-1 cm-2, that is, by 20%. Since bafilomycin is considered to be a specific inhibitor for V-type H(+)-ATPase, these data establish 1) the existence of this type of transport in the rat proximal tubule and 2) that approximately a fifth of the total proximal bicarbonate reabsorption is due to this mechanism of transport.
Ulate
G
G
Departamento de Fisiologia e Biofisica, Universidade de São Paulo, Brasil.
Fernandez
R
R
Malnic
G
G
D000042:Absorption; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001639:Bicarbonates / Q000493:pharmacokinetics*; D001693:Biological Transport, Active; D004594:Electrophysiology; D005260:Female; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007687:Kidney Tubules, Proximal / Q000201:enzymology / Q000378:metabolism*; D018942:Macrolides; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D010477:Perfusion; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D000900:Anti-Bacterial Agents; D001639:Bicarbonates; D018942:Macrolides; C040929:bafilomycin A1; D006180:Proton-Translocating ATPases