Dopaminergic reduction of intracellular calcium: the role of calcium influx.
The effects of dopamine (DA) on 45Ca2+ ion movement and prolactin release in dispersed female rat anterior pituitary cells were studied to elucidate the mechanism for DA reduction of intracellular calcium levels. In 45Ca2+ prelabeled cells, DA inhibited fractional calcium efflux and prolactin release simultaneously and continuously in a concentration-dependent manner (IC50 20 nM DA). We then studied unidirectional calcium influx and observed haloperidol-reversible, concentration-dependent DA suppression of calcium influx into unlabeled cells. These data complement and extend reported fluorescent dye studies and suggest that dopamine primarily inhibits calcium influx, thereby reducing intracellular calcium levels, which leads to suppression of prolactin release and is manifest secondarily as a reduction in fractional 45Ca2+ efflux.
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Department of Neurology, University of Virginia School of Medicine, Charlottesville 22908.
Judd
A M
AM
MacLeod
R M
RM
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D004298:Dopamine / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism*; D051381:Rats
D002132:Calcium Radioisotopes; D011388:Prolactin; D002118:Calcium; D004298:Dopamine