AJP - Cell Physiology, Vol 257, Issue 3 C419-C426, Copyright © 1989 by American Physiological Society
Effect of pH on growth of mouse renal cortical tubule cells in primary culture
S. S. Blumenthal, D. L. Lewand, M. A. Buday, N. S. Mandel, G. S. Mandel and J. G. Kleinman
Department of Medicine, Medical College of Wisconsin, Milwaukee.
We examined the effect of the medium pH on growth of primary cultures of
mouse cortical tubule cells grown in defined medium. A significantly higher
DNA content was observed within 24 h of lowering medium pH from 7.4 to 6.8
or 7.1 and persisted for the duration of the study. Further studies
revealed that either medium acidification or insulin plus prostaglandin E1
nearly doubled uptake of [3H]thymidine in cells deprived of other growth
factors for the previous 72-110 h. Moreover, the effects of insulin,
prostaglandin E1, and medium acidification on [3H]thymidine uptake of
quiescent cells were additive. An alkaline medium pH appeared to have a
small but significant effect on cell hypertrophy, since cells exposed to pH
7.4 and 7.7 had a higher protein-to-DNA ratio than cells incubated at a
lower pH. Cell pH of monolayers grown on glass slides determined from
fluorescence of the carboxyfluorescein analogue
2',7'-biscarboxyethyl-5(6)-carboxyfluorescein (BCECF) was linearly
correlated with medium pH, and changes in medium pH resulted in changes in
steady-state cell pH of a similar magnitude. Four hours after medium
acidification, relative increases in cell Na+ and water content occurred,
whereas medium alkalinization led to decreases in cell Na+ and water
content. The increases in cell Na+ and cell water content at pH 6.8 could
be inhibited by amiloride. We conclude that decreasing the cell pH can be a
mitogenic stimulus for renal tubule cells. Medium acidification is
accompanied by changes in cell Na+ transport, which may be mediated in part
by altered Na+-H+ antiporter activity.
