AJP - Endocrinology and Metabolism, Vol 248, Issue 1 15-E19, Copyright © 1985 by American Physiological Society
Reserpine is a calcium channel antagonist in normal and GH3 rat pituitary cells
I. S. Login, A. M. Judd, M. J. Cronin, T. Yasumoto and R. M. MacLeod
Reserpine exerts direct effects on several tissues, including inhibition of
hormone release from rat anterior pituitary cells. To test the hypothesis
that reserpine may be acting as a calcium channel antagonist, normal or GH3
rat anterior pituitary cells were preincubated in reserpine or the
conventional calcium channel blocker, D-600, followed by exposure to 45Ca2+
together with stimulants of calcium uptake: maitotoxin, a potent calcium
channel activator; A23187, a calcium ionophore; or 50 mMK+. After
incubation, the cells were harvested by vacuum filtration and
cell-associated radioactivity determined. In normal cells, reserpine
blocked both basal and K+-stimulated calcium uptake. Reserpine selectively
blocked maitotoxin but not A23187-induced calcium uptake. In GH3 cells 9
microM reserpine and 30 microM D-600 were equally effective in blocking
maitotoxin-stimulated calcium uptake. Reserpine appears to block
voltage-dependent calcium channels in pituitary cells in a
concentration-dependent manner but not calcium uptake caused
nonspecifically by A23187.
