Phospholipases and the effect of prolactin on uridine incorporation into RNA in mammary gland explants of mice.

The possible effects of phospholipase A and phospholipase C on the rate of uridine incorporation into RNA in mammary gland explants of mice were tested. Phospholipase C had no effect on the rate of uridine incorporation, but it did suppress the action of prolactin on this metabolic parameter. In contrast, phospholipase A was found to stimulate the rate of uridine incorporation into RNA in a manner similar to that of prolactin. The time-courses for the onset of the prolactin and phospholipase A effects were the same. Also, the phospholipase A effect was nonadditive to the effect produced by a maximally stimulatory concentration of prolactin. Finally it was observed that, like the prolactin effect, the phospholipase A effect was abolished by incubation with dibutyryl cyclic AMP, theophylline, quinine, indomethacin and prostaglandin E1. Further, the phospholipase A effect was nonadditive to the prolactin-like effects produced by the cyclic GMP, prostaglandin F2alpha or arachidonic acid. These data therefore suggest that prolactin and phospholipase A stimulate RNA synthesis in mammary gland explants via similar processes.