Temperature dependence of transepithelial potential in isolated perfused rabbit proximal tubules

The response of the transepithelial potential to rapid cooling in isolated perfused proximal convoluted (PCT) and proximal straight (PST) tubules has been studied. Tubules were perfused with solutions which simulated glomerular filtrate (A), filtrate minus glucose and alanine (B), and late proximal tubular fluid (C). The values of the potentials at 37 and 10 degrees C as well as the temperature-sensitive component were found to vary with perfusate composition. Temperature sensifound to vary with perfusate composition. Temperature sensitivity in PCT was seen only when glucose and alanine were present in the perfusate. In contrast, a portion of the potential difference in PST was temperature dependent under each of the perfusion conditions. Temperature sensitivity in PST was inhibited by 10(-5) M ouabain in the bath. It is concluded that the lumen-negative, temperature-sensitive component of PCT potential may reflect the coupled luminal entry of Na+ along with glucose and alanine. In PST, the temperature-sensitive component can be associated with Na+ transport but is not dependent on luminal concentrations of glucose, alanine, HCO3- or Cl- over the ranges examined. Potentials in both segments at 10 degrees C are interpreted as resulting from processes that are passive in nature.