SYNTHESIS AND SECRETION OF CASEINS BY THE MOUSE MAMMARY-GLAND - PRODUCTION AND CHARACTERIZATION OF NEW POLYCLONAL ANTIBODIES

Polyclonal antibodies to mouse alpha- and beta/gamma-caseins were rais ed in rabbits. These antibodies display tissue- and species specificit y as shown by immunoblotting. Immunohistochemical analyses demonstrate that both alpha- and beta/gamma-caseins were synthesized and secreted from virtually all lactating mammary epithelial cells, in a pattern v ery similar to that of the mouse alpha-lactalbumin. Residual amounts o f caseins were located also in the apical surface of epithelial cells surrounding the ducal lumen of virgin mammary gland sections. In contr ast to the significant level of gamma-casein in the milk, the amount o f this protein compared to alpha- or beta-caseins was extremely low in medium conditioned for 24 h by mammary explants of mid-pregnant mice immediately after explantation or after 4 days.