Vitamin D Stimulates Prolactin Synthesis by Ch4c1cells Incubated in Chemically Defined Medium

GH4C1 cells were evaluated as a model system for the investigation of the cellular and molecular mode of action of vitamin D. When cells were incubated in hormone-free, chemically defined medium, the metabolite 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) potently stimulated PRL synthesis (ED50 = 2 x 10(-10) M) with minimal effects on GH synthesis. The stimulation of PRL synthesis was vitamin D metabolite specific. The effect of 1,25-(OH)2D3 was dependent on the addition of extracellular calcium in the concentration range up to 0.1 mM. These results indicate the potential usefulness of this experimental system for the study of vitamin D action.