150-kDa proteins in dog serum bind 1.5-kDa growth-promoting factors for androgen-independent canine prostatic epithelial cells.

Fractions obtained by gel filtration or ultrafiltration of dog serum were tested for their mitogenic activity on canine prostatic epithelial cells: two prostatic growth factor (PGF) entities were found, a major one of 150 kDa (PGF-I) and a minor one of 1.5-2.0 kDa (PGF-II). Treatment and/or extraction with acetic acid, hydrochloric acid, or acidified-ethanol or preparations enriched in PGF-I obtained either by ion-exchange chromatography, acetone precipitation, or retention by ultrafiltration membrane (cut-off 30 kDa) resulted, upon gel filtration, in the detection of a mitogenic activity eluting mainly at the position of PGF-II. Acid hydrolysis and proteolysis of PGF-II led to a loss of activity. It is proposed that, in dog serum, mitogenic peptides for prostatic epithelial cells of 1.5 kDa (PGF-II) are found in their free form and/or in association with proteins of 150 kDa (PGF-I).