AJP - Renal Physiology, Vol 252, Issue 1 74-F82, Copyright © 1987 by American Physiological Society
Calcium-activated phospholipase C associated with canine renal basolateral membranes
S. A. Rogers and M. R. Hammerman
To determine whether calcium-activated phospholipase C effects breakdown of
phospholipids present in the basolateral membrane of the renal proximal
tubular cell we incubated proximal tubular basolateral membranes isolated
from dog kidney in the absence and presence of deoxycholate, and varied
free calcium from 0 to 300 microM. Following incubations, lipids were
extracted from membranes and separated using thin-layer chromatography. In
the absence of deoxycholate, neither phosphatidylinositol nor diglyceride
extractable from basolateral membranes changed significantly as calcium was
increased. In the presence of deoxycholate, extractable
phosphatidylinositol and diglyceride did not change significantly as free
calcium was elevated from 0 to 0.03 microM, but phosphatidylinositol
decreased and diglyceride increased progressively as 0.03-300 microM free
calcium was included in incubations. Most of the increased extractable
diglyceride could be accounted for by hydrolysis of phosphatidylinositol as
reflected by decreased extractable phosphatidylinositol. Our findings
suggest that calcium-activated phospholipase C effects breakdown of
phospholipids present in the basolateral portion of the plasma membrane of
the renal proximal tubular cell. It is possible that this enzyme plays a
role in stimulating protein kinase c at this site.
