DIRECT MITOGENIC EFFECTS OF INSULIN, EPIDERMAL GROWTH-FACTOR, GLUCOCORTICOID, CHOLERA-TOXIN, UNKNOWN PITUITARY FACTORS AND POSSIBLY PROLACTIN, BUT NOT ANDROGEN, ON NORMAL RAT PROSTATE EPITHELIAL-CELLS IN SERUM-FREE, PRIMARY-CELL CULTURE

Abstract

Selective nutritive conditions were used to isolate normal epithelial cells from fibroblasts in primary cell cultures prepared from adult rat prostate. The pure population of normal epithelial cells proliferated at an exponential rate on a simple polystyrene substratum with doubling times of 35-50 h for 10-12 days in the absence of high epithelial cell density, other cell types, or added extracellular matrix elements. Optimization of the nutritive environment allowed direct analysis of the hormone: growth factor requirements for sustained proliferation of the isolated epithelial cells in serum-free medium. An in situ videometric method was used to assay the effect of over 30 known hormones and growth factors on proliferation of the prostate epithelial cell population. The results revealed direct mitogenic effects of insulin, epidermal growth factor, glucocorticoid, cholera toxin, 1 or more unidentified factors from bovine pituitary and possibly prolactin. No direct mitogenic effect of androgen on isolated prostate epithelial cells could be demonstrated. Radioimmunoassay of androgen in the primary cultures showed that endogenous androgen was about 34 pM on day 1 of culture and thus probably too low to mask a response to exogenous androgen. Deletion of any single active growth factor did not reveal an androgen response. The results demonstrate a nultihormonal control of normal prostate epithelial cell maintenance and proliferation without the direct participation of androgen.