SERUM AND PROSTATIC GROWTH-PROMOTING FACTORS FOR STEROID-INDEPENDENT EPITHELIAL-CELLS OF ADULT DOG PROSTATE

A growth factor-like effect has been observed on canine prostatic epithelial cells when cultured in the presence of their homologous serum and prostatic extracts; the mitogenic activities of both preparations were dose-dependent and not altered by charcoal treatment. The effect of dog serum decreased when the density of the epithelial cell cultures increased and was minimal on canine prostatic fibroblasts. Trace amounts of intracellular sex steroids did not contribute to epithelial cell proliferation since the presence of sex steroid action inhibitors did not alter growth rate; in those conditions, cycloheximide completely prevented cell division. When various hormones and known mitogenic agents were tested alone or in combination with steroids, none elicited an increase in the number of epithelial cells cultured in serum-free medium or altered the proliferative effect of dog serum observed in parallel cultures. On gel filtration, dog serum or tissue cytosol showed a major mitogenic activity at an apparent molecular mass of 150 kDa and a minor one of 1.5 kDa as evaluted by gel filtration of dog serum ultrafiltrate. Acidic extraction of prostatic tissue followed by chromatography on a hydrophobic C-18 column and subsequent gel filtration also led to the detection of the low M(r) component. Thus, humoral and/or tissular factors present in vivo and different from known mitogens may be of importance as direct modulators of the basal epithelial cell growth in the adult canine prostate.