Isolation and Characterization of Chromogranins A, B, and C from Bovine Chromaffin Granules and a Rat Pheochromocytoma

Bovine chromaffin granules from adrenal medulla contain three acidic secretory proteins: chromogranins A, B, and C. For isolation of these proteins, methods based mainly on high performance liquid chromatography were developed. After removal of contaminating glycoproteins by lectin affinity chromatography, chromogranins were separated by high performance anion-exchange, gel-filtration, and reverse phase liquid chromatography. As a final purification step sodium dodecyl sulfate-gel electrophoresis was performed. Amino acid analysis of isolated bovine chromogranins revealed a similar composition of all three proteins, with glutamic acid being the most prominent amino acid. The methods developed for bovine proteins also proved suitable for isolating rat chromogranins A and B from a transplantable pheochromocytoma. Chromogranin C was not present in sufficient amounts to be isolated from this tissue. The chromogranins purified by these methods were used to raise specific antibodies in rabbits. The use of purified chromogranins together with specific antisera may be valuable in understanding the still undiscovered function of these proteins.