Primary culture of rat mammary epithelial cells. I. Effect of plating density, hormones, and serum on DNA synthesis.

Methods for the primary culture of rat mammary epithelial cells and the response of these cells to various hormones and culture parameters are described. In addition, the techniques for subsequent retransplantation of cultured cells into cleared fat pads of isogenic hosts as a test for normalcy of cultured tissue are detailed. A characteristic and reproducible course of the culture was followed for 2 weeks, after which rat mammary epithelial cells ceased to proliferate and were eventually overgrown by fibroblast-like cells. During the initial 2 weeks in culture, mammary cells and contaminating fibroblast-like cells were responsive to polypeptide and steroid hormones and the percentage of proliferating mammary cells could be enhanced with insulin, prolactin, estradiol, progesterone, and hydrocortisone.