The dopaminergic regulation of anterior pituitary 45Ca2+ homeostasis and prolactin secretion.
A role for the regulation of cellular Ca2+ homeostasis in the dopaminergic control of prolactin secretion was investigated in rat anterior pituitary glands. Withdrawal of dopamine stimulated the uptake of 45Ca2+ into hemipituitary tissue by 48% after 3 min. Radioisotope desaturation from tissue prelabelled with 45Ca2+ was significantly retarded in the presence of dopamine. Withdrawal of dopamine rapidly stimulated 45Ca2+ efflux from prelabelled tissue by 79% and was accompanied by a three- to fourfold rise in prolactin secretion. The 45Ca2+ efflux response to dopamine withdrawal was reduced in tissue prelabelled in the presence of dopamine. Agonist displacement with metoclopramide mimicked the effect of dopamine withdrawal on 45Ca2+ efflux and prolactin secretion. These observations demonstrate that the stimulation of prolactin release by dopamine withdrawal is accompanied by a redistribution of cellular Ca2+ and support the hypothesis that dopamine inhibits secretion by decreasing Ca2+ influx in the mammotroph cell.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D004298:Dopamine / Q000502:physiology*; D005260:Female; D006706:Homeostasis / Q000187:drug effects; D066298:In Vitro Techniques; D008787:Metoclopramide / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000378:metabolism / Q000502:physiology*; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D011917:Rats, Inbred Lew; D013997:Time Factors
D002132:Calcium Radioisotopes; D011388:Prolactin; D008787:Metoclopramide; D002118:Calcium; D004298:Dopamine