Rapid interaction of prolactin with mouse mammary gland explants.

Exposure of mouse mammary gland explants to prolactin at 0 degrees C, for periods as brief as 10 seconds, caused a stimulation of labeled uridine incorporation into RNA during a subsequent incubation for 4 h at 37 degrees C. Furthermore, a 2-h wash of the prolactin-exposed explants in media at 0 degrees C did not attenuate the hormonal effect. A similar exposure of explants to insulin, followed by a 2-h wash at 0 degrees C, caused the abolition of the insulin stimulation of labeled uridine incorporation into RNA. The results suggest that there is a rapid and relatively stable interaction of prolactin with the mammary gland, while the interaction of insulin with this tissue would appear to be less stable.