AJP - Renal Physiology, Vol 251, Issue 6 1018-F1028, Copyright © 1986 by American Physiological Society
Effects of vasoactive peptides on cytosolic calcium in cultured mesangial cells
A. Hassid, N. Pidikiti and D. Gamero
We have used the "second generation" Ca indicator, fura-2, to measure
cytosolic free Ca concentrations in superfused cultures of adherent primary
renal mesangial cells. The basal cytosolic free Ca concentration in these
cells was found to be 93 +/- 5 nM (n = 35). The Ca ionophore ionomycin (0.1
microM) increased cytosolic Ca levels to a peak value of fourfold above
basal, followed by a decline to a steadily maintained concentration of
twofold above basal. Two vasoactive peptide hormones, arginine vasopressin
and angiotensin II, at maximally effective concentrations, transiently
increased cytosolic free Ca levels to peak values of three- and sixfold,
respectively, above basal levels. The angiotensin II-evoked increase
declined to near basal values before rising again to a value of 1.5- to
2-fold above basal. Cells treated with vasopressin did not have a
significant secondary increase of Ca above a small, time-dependent,
spontaneous increase. Mesangial cells demonstrated tachyphylaxis to both
peptides. However, cross-tachyphylaxis was not observed. Treatment of cells
with angiotensin II in
ethyleneglycol-bis-(beta-aminoethylether)-N,N'-tetraacetic
acid-supplemented Ca-deficient medium, or with the Ca channel blockers
nifedipine or verapamil, did not eliminate the transient phase of cytosolic
Ca metabolism. In contrast, the Ca channel blockers completely inhibited
the second sustained Ca response to angiotensin II. These results indicate
that angiotensin II and vasopressin mobilize intracellular Ca in cultured
adherent mesangial cells. Angiotensin II, but not vasopressin, also appears
to increase cytosolic Ca by influx of extracellular Ca through specific
channels.
