Calcium and insulin in the regulation of DNA synthesis in mouse mammary gland studied in organ culture

The interaction of calcium and insulin was investigated in mouse mammary gland organ culture by analysis of the time-course of the DNA-synthetic response following delayed addition of insulin or calcium to the culture media. The DNA-synthetic responses were also studied using mammary expiants from virgin, pregnant and lactating mice. These experiments have shown that qualitative differences exist in the responsiveness of mammary epithelium to insulin and calcium. Thus, although it is evident that in mammary epithelium calcium modifies the DNA-synthetic response to insulin, the present data do not support the concept that Ca 2+ is the intracellular mediator of insulin action.