Cyclic Nucleotides and the Effect of Prolactin on Uridine Incorporation into RNA in Mammary Gland Explants of Mice[*]

Abstract

Studies were carried out to determine whether the action of prolactin on uridine incorporation into RNA in gland explants may be mediated by one or more of the cyclic nucleotides. It was discovered that cGMP had prolactin-like effects on uridine incorporation into RNA. In contrast, the effect of prolactin on uridine incorporation was completely suppressed by incubation with DBcAMP or with inhibitors of cyclic nucleotide phosphodiesterase including theophylline and quinine. The data therefore suggest that the effect of prolactin on uridine incorporation into RNA may be mediated by an elevated concentration of cGMP and perhaps a reduced or maintained concentration of cAMP.

In contrast to prolactin, the effect of insulin on uridine incorporation in the mammary gland does not appear to be mediated by the cyclic nucleotides. Neither DBcAMP, cAMP, cGMP nor inhibitors of cyclic nucleotide phosphodiesterase suppressed the effects of insulin on uridine incorporation into RNA. Furthermore, none of these agents had insulin-like effects which could be causally related to the actions of insulin. Although cAMP had both insulin-like and prolactinlike effects on uridine metabolism, an elevated concentration of cAMP does not appear to mediate the actions of either of these hormones because of reasons cited in the discussion.

Key words

Prolactin - Uridine Incorporation - RNA - cGMP - cAMP

1 This investigation was supported by NIH grant number HD 06571-01 from the National Institutes of Child Health and Human Development, U.S.A.

1 This investigation was supported by NIH grant number HD 06571-01 from the National Institutes of Child Health and Human Development, U.S.A.