Partial purification of a prostatic growth factor

A 5-step fractionation procedure was used to isolate a prostatic growth factor from a tissue homogenate of human benign prostatic hyperplasia. The procedure made use of the property of prostatic growth factor to occur predominately as a large molecule (greater than 67,000) in low ionic strength solution (Tris with 0.05 M NaCl) but as a smaller molecule (less than 33,000) in high salt buffer (Tris with 1.55 M NaCl). The fractionation scheme consisted of ammonium sulfate precipitation, gel filtration (low ionic strength) and DEAE chromatography. The growth factor activity was eluted from DEAE with high ionic strength buffer followed by 2 gel filtration steps in high ionic strength buffer. The fractionation scheme produced greater than a 200-fold increase in prostatic growth factor activity and 10 per cent recovery. Additional separation steps will be required to purify prostatic growth factor to homogeneity.