Changes in insulin and prolactin responsiveness of goat mammary tissue during ontogenesis and pregnancy

Mammary tissue of goats in different stages of ontogenesis and pregnancy were organ cultured and their insulin and prolactin responsiveness was studied. Based on the synthesis of DNA in the presence of insulin and tissue secretory responses to prolactin, the responsive tissues were found in young goats up to 3 month of age (prolactin responsive only up to 24 days of age), in mature virgin goats at the end of breeding season, mature virgin goats with precocious lactation and in nulliparous goats from the 8th week of pregnancy. Unresponsive tissues were found in goats from 4.5 month of age to the maturity. The high number of antral follicles in goat ovaries was found to be coincident with high mammary insulin and prolactin responsiveness during ontogenesis. It appears that ovarian and placental steroids and placental lactogen render the goat mammary tissue responsive to insulin and prolactin in organ culture.