AJP - Cell Physiology, Vol 261, Issue 6 C1115-C1122, Copyright © 1991 by American Physiological Society
Potassium transfer assay for cell communication: effects of phorbol esters, retinoic acid, and furosemide
M. L. Ledbetter, P. L. Medrek and B. M. Spinney
Department of Biology, College of the Holy Cross, Worcester, Massachusetts 01610.
Using a mass culture assay for the contact-dependent transfer of potassium
among cells with intrinsic differences in ability to concentrate it, we
have investigated the ability of several drugs to influence this form of
cell communication. We concentrated on 12-O-tetradecanoylphorbol-13-acetate
(TPA), which is known to interfere with gap junction-mediated communication
and ion transport in several other systems, and compared its effects with
those of its inactive derivative, 4-O-methyl-TPA. We found that the
communication between mouse BALB/c 3T3 cells and human diploid fibroblasts
was reduced in the presence of TPA but not O-methyl-TPA and that this
inhibition was not obscured by small but measurable influences of TPA on
steady-state content and transport of 86Rb+. We confirmed these findings
using an autoradiographic assay for transfer of uridine derivatives among
cells in contact. We also showed that retinoic acid had no effect on
communication in the ion transfer assay but that furosemide, an inhibitor
of Na(+)-K(+)-2Cl- cotransport, stimulated ion transfer dramatically both
in the presence and absence of TPA. These results indicate both the promise
and the limitations of the potassium transfer assay for identifying
potential modulators of gap junction-mediated cell communication.
