Chromatographic studies on corticotropin

Abstract

Corticotropin concentrates were chromato-graphed on a carboxylic resin in sodium phosphate buffer. Active components were resolved. The elution volumes are reproducible on chromatography of the isolated components. Methods were used for isolating the active components from salt solutions, such as the buffers used in chromatography, which depend on the adsorption of the material on a carboxylic resin at pH 3 or on extraction of the material in phenol. The main active component was designated corticotropin A1. Other components (corticotropins A2 and A3) are present which are less retarded on the resin columns and their amount may be increased under certain conditions. Alkali converts corticotropin A1 into A2. Cortico-tropins A1 and A2 can be distinguished by ionophoresis on paper. When corticotropin A1 is treated with pepsin, inactivation does not occur, but a group of new substances, termed collectively corticotropin B1, is produced. The B1 components are separable by ionophoresis on paper. A different family (B2) is produced from corticotropin A2. Alkali converts the corticotropin B1 family into the B2 family, a change analogous to that of A1 to A2. The effects of the cation concentration and pH of the buffer and of the particles size of the resin on the chromatographic elution volumes are described. From the method of isolation it seems that corticotropin A1 is identical with the corticotropin A previously described by other workers.