Abstract

Mechanisms of oestrogen stimulation of mammary development were examined using ewe lambs treated with oestradiol (0.1mg/kg BW/day for 7 days; n=5) or controls (n=5). Mammary explants were incubated with [3H]- thymidine to determine effects of oestrogen on epithelial cell proliferation. Also, explants of mammary stroma and parenchyma were co-cultured with a mammary epithelial cell line (MAC-T) to determine the ability of the explants to stimulate MAC-T growth. Oestrogen increased proliferation of ewe mammary epithelial cells (P < 0.02). In co-cultures, addition of mammary explants increased growth of MAC-T cells (P < 0.01), but there was no effect or interaction of tissue type (stroma vs. parenchyma) or oestrogen (P > 0.10). Proliferation of mammary explants was negatively correlated with growth of MAC-T cells in co-cultures (r = -0.41; P < 0.07). These results confirm the importance of oestrogen and mammary stroma in regulating mammary epithelial proliferation but fail to show a requirement for mammary stroma to mediate oestrogenic effects on epithelial cells.

S, Ellis, TB McFadden, and RM Akers

Proceedings of the New Zealand Society of Animal Production, Volume 56, , 62-64, 1996