6-Dimethyl amino purine and 2-amino purine inhibit the induction of expression of milk protein genes by prolactin

Two protein kinase-inhibitors, 6-dimethyl amino purine and 2-amino purine inhibited induction of beta-casein synthesis by Prolactin when added to the culture medium of rabbit mammary explant and cells. The accumulation of the mRNA for alpha s1- and beta-caseins and for whey acidic protein did not take place in the presence of the inhibitors whereas beta-actin mRNA concentration was not altered. In the same experimental conditions, H7, an inhibitor of protein kinase C and, to a lower extent, of protein kinase A did not prevent Prolactin from acting. These data suggest for the first time that specific protein kinases are involved in the transduction of the Prolactin signal to milk protein genes.