SYNTHESIS OF GELATINASES BY RAT MAMMARY EPITHELIAL AND MYOEPITHELIAL CELL-LINES

The synthesis of metalloproteinases capable of degrading the basement membrane is an important factor contributing to the involution of the mammary gland after the young are weaned. To investigate the cellular source of mammary gland metalloproteinases, we have studied the synthe sis of gelatinases by rat mammary epithelial and myoepithelial cell li nes immortalized with a temperature-sensitive T-antigen. At 39.5 degre es C, the temperature at which the cells display increased differentia ted characteristics, myoepithelial cells synthesize 40- to 160-fold gr eater amounts of three gelatinases (M(r)s-72, 92, and 135 kDa) than ep ithelial cells. The gelatinases are preferentially secreted through th e basolateral surface of myoepithelial cells. Growth of cells in the p resence of a variety of growth factors and cytokines demonstrates the differential regulation of the synthesis of the 72- and 92-kDa gelatin ases. These results suggest that the myoepithelial cell is a major sou rce of mammary gland metalloproteinases. (C) 1994 Academic Press, Inc.