AJP - Cell Physiology, Vol 253, Issue 2 C343-C347, Copyright © 1987 by American Physiological Society
Cl(-)-selective microelectrodes: sensitivity to anionic Cl- transport inhibitors
A. C. Chao and W. M. Armstrong
Cl(-)-selective microelectrodes, containing Corning code 477315 or 477913
liquid ion exchangers, are often used to measure extra- and intracellular
Cl- activities in the presence of Cl- transport inhibitors such as
furosemide, bumetanide, and the stilbene sulfonic acid derivative
4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS). Because
these inhibitors are anions in the physiological pH range and have
relatively high lipid solubilities, they would be expected to interfere
with the response to Cl- of these microelectrodes. Preliminary reports have
confirmed this expectation. We examined the effect of furosemide,
bumetanide, and SITS on the Cl(-)-selective barrels of double-barreled
microelectrodes containing Corning code 477315 liquid anion exchanger and
suitable for impaling small cells (e.g., epithelial cells). The results
showed that at pH 8.2 in pure solutions of furosemide and bumetanide, these
microelectrodes gave linear responses to the logarithm of furosemide or
bumetanide concentrations ranging from 1 X 10(-2) to 1 X 10(-4) M. In the
physiological pH range both these inhibitors (in concentrations of 0.1 mM)
interfered significantly with the response of the microelectrodes to Cl-
(in concentrations ranging from 100 to 1 mM). Calculated electrode
sensitivities, relative to Cl-, were approximately 150 for both these
compounds. Microelectrodes of this type appeared to be approximately 1,000
times as sensitive toward SITS as they were toward Cl-.
