150‐kDa Proteins in Dog Serum Bind 1.5‐kDa Growth‐Promoting Factors for Androgen‐Independent Canine Prostatic Epithelial Cells

Abstract

ABSTRACT 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 of 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).