Effect of Mammary-Derived Growth Inhibitor on Proliferation of MAC-T Bovine Mammary Epithelial Cells

¹ Department of Animal Science Lactation Physiology Laboratory Cornell University Ithaca, NY 14853
² Department of Animal Science McGill University Ste. Anne de Bellevue, PQ, Canada H9X 3V9
³ Max Delbruck Center for Molecular Medicine Berlin, Germany 1115

An established bovine mammary epithelial cell line (MAC-T) was used as a model to examine the effect of mammary-derived growth inhibitor on mammary epithelial cell proliferation. Prior to each proliferation assay, cells were synchronized in G₁/G₀ by culturing for 24 h without serum. Flow cytometry revealed that 90% of cells were in G₁/ G₀, 4% in G₂/M, and 6% in the S-phase after serum deprivation. Approximately 2 x 10³ cells per well were seeded onto 24-well plates. Cells were incubated for 5 to 6 d with various amounts of mammary-derived growth inhibitor (0 to 100 ng/ml). Mammary-derived growth inhibitor and medium were changed daily. Mammary-derived growth inhibitor decreased mammary epithelial cell proliferation at .l ng/ml. Synchronization of cells in G₁/G₀ was necessary for inhibition of cell proliferation. Cells not arrested by serum deprivation were not responsive to mammary derived-growth inhibitor. Inhibition of cell proliferation was transient and observed up to 96 h in culture. Mammary-derived growth inhibitor appears to act in vitro by inhibiting the resumption of stationary cell proliferation following starvation.

Key Words: mammary-derived growth inhibitor • epithelial cells • MAC-T cells

Submitted on February 19, 1993
Accepted on August 9, 1993