Prolactin-like activity of anti-prolactin receptor antibodies on casein and DNA synthesis in the mammary gland.

Publisher Website
Google Scholar
Abstract
Prolactin [PRL] receptors were partially purified from rabbit mammary gland membranes by using an affinity chromatography technique. Antibodies against this PRL receptor preparation were obtained in guinea pig and sheep. Both antisera were able to inhibit the binding of 125I-labeled ovine PRL to rabbit mammary gland membranes. When added to culture media of rabbit mammary explants, the anti-PRL receptor antiserum inhibited the capacity of PRL to initiate casein synthesis and casein mRNA accumulation as a function of the antiserum concentration. In the absence of PRL, both antisera (guinea pig and sheep) at moderate concentrations were capable of mimicking PRL action on casein gene expression and on DNA synthesis. At higher concentrations, the anti-PRL receptor antibodies inhibited their own actions. Several characteristics of the PRL effect were also observed with the anti-PRL receptor antibody: the stimulatory effect of the antibody was amplified by glucocorticoids; colchicine, which was capable of blocking PRL action, also prevented the induction by the antibody. Lysosomotropic agents, which do not interfere with PRL action, did not alter the response observed with the antibody. An anti-PRL receptor antibody apparently can mimic 2 major actions of PRL obtained in mammary explant culture. The PRL molecule evidently is not required beyond the initial binding to its receptor.