Effects of prostaglandins on RNA and casein synthesis in mammary gland explants of mice.

Prostaglandins B2, E2, and F2alpha were found to stimulate RNA synthesis in mammary gland explants of mice in a prolactin-like manner. These effects were non-additive to maximally stimulatory concentrations of prolacin. Also, time-course studies showed that the effects of these prostaglandins only became apparent following at 2-4 hour lag period. The effects of these prostaglandins were not observed in explants which were not pretreated with insulin plus hydrocortisone, i.e., in tissues not responsive to prolactin Prostaglandins E1, A2, A1, B1, and F1alpha had no effects on the rate of RNA synthesis, but each of these prostaglandins abolished the responsivitiy of the explants to prolactin. Since DBcAMP, theophylline, and indomethacin were found previously to suppress the aciton of prolactin on RNA synthesis, the effects of these agents on the stimulatory effects of prostaglandins B2, E2, and F2alpha were tested. The incubation of explants with 5 mM DBcAMP or 5 mM thophylline abolished the effects of these prostaglandins on RNA synthesis. But incubation with indomethacin did not affect the responses to these prostaglandins. Prolactin-like effects of prostaglandins on casein synthesis were not observed. Prostaglandins E1, A2, A1, B2, F1alpha and indomethacin did, however, abolish the prolactin stimulation of casein synthesis. Furthermore, the preincubation of explants with prostaglandins B2, E2, F2alpha or arachidonic acid significantly shortened the time of onset of the prolactin stimulation of casein synthesis. The results are discussed with regard to a possible role of the prostaglandins as mediators for the actions of prolactin in the mammary gland.