Regulation of prolactin expression in leukemic cell lines and peripheral blood mononuclear cells.

To address the role of different intracellular signals in prolactin (PRL) expression in leukocytes, we have investigated the effects of chlorophenylthio-cAMP (cptcAMP), phorbol myristate acetate (PMA) and ionomycin on the activation of the upstream PRL promoter in several leukemic cell lines. All three stimulators, alone or in synergism with each other, were able to modulate promoter activity, but their actions were cell-type dependent. In freshly isolated peripheral blood mononuclear cells (PBMC), PRL expression could only be stimulated by cptcAMP. The physiological importance of cAMP in the regulation of PRL expression in leukocytes is suggested by the finding that in PBMC, PRL expression is enhanced by prostaglandin-E(2) and the beta(2)-adrenergic agonist terbutaline, which both signal through cAMP.