EVOLUTION OF INSULIN-LIKE GROWTH-FACTOR-I, PROSTAGLANDIN E(2), AND MITOGENIC ACTIVITY OF BOVINE MAMMARY PRIMARY LYMPH DURING THE DRY PERIODAND LACTOGENESIS

Four pregnant cows near the end of lactation were fitted with a cathet er in a lymph duct afferent to the supramammary lymph node. Cows were dried off 3 d after surgery, and samples of lymph were collected daily from the day of surgery until 4 d postpartum. Samples of blood and ma mmary secretions were taken before and after drying off and at parturi tion. Concentrations of most metabolites were lower in lymph than in s erum. Concentrations of IGF-I and prostaglandin E(2) were not affected at drying off but decreased and increased, respectively, at parturiti on. All IGF-binding proteins that were present in serum were also pres ent in lymph fluid, but the binding activity was lower. Mitogenic acti vities of lymph samples taken at various physiological stages were det ermined on mammary epithelial (MAC-T) and fibroblast cell lines. Lymph was mitogenic, but mitogenic activity was not related to physiologica l stages. The correlation was high between mitogenic activity of lymph on MAC-T cells and the content of prostaglandin E(2) in lymph. Supple mentation of lymph with additional prostaglandin E(2) increased mitoge nic activity, and neutralization of lymph by antibodies reduced mitoge nic activity. Basal medium conditioned by the epithelial cell line con tained 100 to 250 pg/ml of immunoassayable prostaglandin E(2).