Partial purification of an adrenal growth factor produced by normal bovine anterior pituitary cells in culture

Abstract

An adrenal growth factor (AGF) was partially purified from the conditioned medium of cultured bovine anterior pituitary cells. This 900-fold purification was accomplished by gel filtration, ammonium acetate precipitation, cation exchange fast protein liquid chromatography, and C8 reverse phase fast protein liquid chromatography. The AGF had an apparent mol wt of 25,000-30,000, as determined by gel filtration chromatography at acid pH. It was tested on mouse fibroblasts (3T3 cells), rat fibroblasts (NRK cells), mouse adrenocortical cells (Y1 cells), and normal bovine adrenocortical cells (BAC cells) and found to be a relatively potent mitogen for BAC cells only, contrasting with fibroblast growth factor, which could stimulate all of these cell types. It is sensitive to reducing agent, alkaline pH, and boiling. Purification steps were carried out at acid pH, suggesting some degree of stability to acidic pH. The mitogenic activity in the conditioned medium could be blocked by ACTH, and the purified AGF contained no ACTH immunoactivity. The AGF appears distinct from epidermal growth factor, since it could not bind to epidermal growth factor receptors, and platelet-derived growth factor, which could not stimulate BAC cells. Purification to homogeneity was not accomplished, because very broad bands of mitogenic activity were observed with all of the chromatographic methods tried. The AGF appears to be distinct from any of the known growth factors.