bafilomycin-a1 and Alkalosis

The loop of Henle (LOH) reabsorbs approximately 15% of filtered HCO3- via a luminal Na(+)-H+ exchanger and H+ATPase. During acute metabolic alkalosis (AMA) induced by i.v. HCO3- infusion, we have observed previously inhibition of LOH net HCO3- reabsorption (JHCO3-), which contributes to urinary elimination of the HCO3- load and correction of the systemic alkalosis. To determine whether the activities of the Na(+)-H+ exchanger and/or H(+)-ATPase are reduced during AMA, two inhibitors believed to be sufficiently specific for each transporter were delivered by in vivo LOH microperfusion during AMA. AMA reduced LOH JHCO3- from 205.0 +/- 10.8 to 96.2 +/- 11.8 pmol.min-1 (P < 0.001). Luminal perfusion with bafilomycin A1 (10(-4) mol.l-1) caused a further reduction in JHCO3- by 83% and ethylisopropylamiloride (EIPA; 5.10(-4) mol.l-1) completely abolished net HCO3- reabsorption. The combination of bafilomycin A1 and EIPA in the luminal perfusate was additive, resulting in net HCO3- secretion (-66.6 +/- 20.8 pmol.min-1; P < 0.001) and abolished net fluid reabsorption (from 5.0 +/- 0.6 during AMA to 0.2 +/- 1.1 nl.min-1; P < 0.001). To establish whether HCO3- secretion via luminal stilbene-sensitive transport mechanism participates in LOH adaptation to AMA, we added diisothiocyanato-2,2'-stilbenedisulphonate (DIDS; 10(-4) mol.l-1) to the perfusate. No effect was found.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Acute Disease; Alkalosis; Amiloride; Animals; Anti-Arrhythmia Agents; Anti-Bacterial Agents; Bicarbonates; Biological Transport, Active; Carbon Dioxide; Loop of Henle; Macrolides; Male; Proton-Translocating ATPases; Rats; Rats, Sprague-Dawley