Hormone-responsive survival of mammary gland explants from the pregnant tammar wallaby (Macropus eugenii) In the absence of exogenous hormones and growth factors

1. 1. The level of β-lactoglobulin mRNA increased maximally in mammary expiants from late pregnant tammars cultured for 3 days in media containing either prolactin or insulin, cortisol and prolactin. 2. 2. The same level of accumulation occurred when expiants were first cultured for 4 days in a chemically defined medium with no exogenous hormones, serum or growth factors, suggesting that the tissue remains viable and hormone-responsive during the initial incubation. 3. 3. Mammary expiants cultured for 4 days in medium with no hormones demonstrated a progressive increase in the rate of RNA and DNA synthesis suggesting that the tissue is under a positive autocrine/paracrine stimulus. © 1991.