AJP - Renal Physiology, Vol 238, Issue 6 491-F498, Copyright © 1980 by American Physiological Society
Effect of collagenase and ouabain on renal cell volume in hypotonic media
M. A. Linshaw and J. J. Grantham
Proximal straight tubules (S2 segments) swell rapidly in hypotonic media,
but within a few minutes their volume returns toward control levels due to
extrusion of K, Na, Cl, and water from the cytoplasm. In the present
studies we determined the extent to which hydrostatic pressure (derived
from the elastic tubule basement membrane (TBM) as the tubule enlarged in
hypotonic medium) contributed to the regulation of cell volume. Removal of
the TBM by collagenase had no effect on cell volume regulation in otherwise
normal tubules. By contrast, tubules treated with ouabain, though they
appeared to regulate their volumes in hypotonic media, were unable to do so
in the presence of glycoside if the TBM had been removed with collagenase.
This latter result is interpreted to show that hydrostatic pressure
generated by extension of the TBM can cause "apparent" volume regulation
when the sodium pump is blocked by ouabain. We conclude that normal
proximal renal tubules regulate cell volume in hypotonic solutions by
mechanisms that are dependent on the normal operation of the classical
sodium pump.
