Intracellular pH of the turtle bladder assessed with fluorescent probes.

Intracellular pH of the turtle bladder was measured with fluorescent probe 6-carboxyfluorescein (6-CF) diacetate. In isolated cells this probe provides reliable, reproducible and fast measurements of intracellular pH. The probe was mainly located in the cytosol and thus the values of intracellular pH mainly reflect cytosolic pH. The values of intracellular pH obtained with 6-CF were very similar to those measured with 14C-methylamine and 'null point' technique. The 6-CF technique was capable of detecting small changes in intracellular pH induced by acetazolamide. The intracellular pH of the mitochondrial-rich and granular cell fraction was not different. In addition to assessing intracellular pH of isolated cells, it was possible to monitor the intracellular pH of whole bladders continuously with 6-CF. Addition of CO2 to serosal solution decreased intracellular pH while perfusion with NH3 increased intracellular pH. Thus, 6-CF provides reliable and accurate measurements of intracellular pH in isolated cells and in whole bladders. This technique is capable of detecting rapid changes in intracellular pH and provides continuous monitoring of intracellular pH and thus should allow correlation of changes in urinary acidification with intracellular H+ concentration.