BINDING OF PROLACTIN TO THE RABBIT MAMMARY GLAND DURING PREGNANCY

Abstract

Binding of prolactin to the rat mammary gland is low during pregnancy and only increases at parturition. Failure to demonstrate binding of prolactin may be related to occupancy of the prolactin receptor by placental lactogen [Holcomb et al., 1976]. However, the rabbit apparently does not produce a placental lactogen and it was therefore of interest to determine whether the results of binding of prolactin to the rabbit mammary gland during pregnancy showed significant differences from those obtained in the rat. The results show a clear difference from the pattern of binding reported in the rat. It is apparent that in the rabbit, the inhibition of lactogenesis until around day 19 of pregnancy and inhibition of full lactation until after parturition is not related to an absence of prolactin receptor in the mammary gland.