AJP - Cell Physiology, Vol 249, Issue 1 105-C110, Copyright © 1985 by American Physiological Society
Extracellular potassium modifies the structure of kidney epithelial cells in culture
S. Waack, M. M. Walsh-Reitz and F. G. Toback
In animals fed a K-deficient diet, alterations in kidney cell structure and
function occur in association with changes in the ionic composition of the
extracellular fluid. The hypothesis that the extracellular K concentration
mediates these changes in renal tissue was tested in cultures of monkey
kidney epithelial cells (BSC-1 line) by reducing the K concentration of the
culture medium from the control value of 5.4 to 3.2 mM. Exposure of BSC-1
cells to low-K medium raised the maximal rate of uptake for L-glutamic acid
by 39% without a change in apparent Km. To determine whether this
alteration in plasma membrane function had a structural correlate, studies
of the cell surface were performed using scanning and transmission electron
microscopy. Morphometric analysis of scanning electron micrographs revealed
that the number of microvilli per cell per unit surface area was 45%
greater in cells exposed to low-K medium for 3 min than those exposed to
control medium. This observation was confirmed by transmission electron
microscopy. The results indicate that an alteration in the extracellular K
concentration per se can modify specific structural and functional
characteristics of kidney epithelial cells.
