AJP - Endocrinology and Metabolism, Vol 249, Issue 4 337-E344, Copyright © 1985 by American Physiological Society
Calcium, cAMP, and dopamine affect single mammotrophs assayed by hemolytic plaques
J. M. Anderson, D. A. Keefer, D. D. Koritnik, T. Yasumoto and M. J. Cronin
We investigated the effects of dopamine, forskolin, and maitotoxin on
prolactin release from individual rat and monkey mammotrophs. Forskolin
increases cAMP levels, whereas maitotoxin amplifies the influx of
extracellular calcium. Prolactin secretion from single mammotrophs was
visualized by the reverse hemolytic plaque assay and then quantified by
measuring the proportion of plaque-forming cells and the mean plaque area.
In the presence of dopamine alone both the plaque proportion and mean area
of the plaques formed by rat mammotrophs decreased by 50 and 40%,
respectively. This inhibition of secretion was blocked by the dopaminergic
antagonist spiperone as well as forskolin and maitotoxin. Forskolin and
maitotoxin alone significantly elevated both the proportion (+30%) and area
(+180% for forskolin and +250% for maitotoxin) of the plaques. These
actions of maitotoxin were neutralized by D-600, a calcium channel blocker.
All of these agents induced similar trends with monkey prolactin cells. We
conclude that single mammotrophs in culture respond to perturbations in a
differential manner and in a way predicted by earlier results based on
macropopulation measurements.
