Immunological studies on the distribution of chromogranin A and B in endocrine and nervous tissues.

Bovine chromaffin granules contain two major families of acidic proteins, chromogranins A and B. The occurrence of these proteins in endocrine and nervous tissue was investigated by immunoblotting (one- and two-dimensional), and by immunohistochemistry. Immunoblotting revealed that in anterior hypophysis and in splenic nerve from ox, immunologically crossreacting proteins are present which in two-dimensional electrophoresis migrate to the same position as adrenal chromogranins A and B. Smaller proteins derived from chromogranin B by endogenous proteolysis were much less prominent in these tissues when compared with adrenal medulla. Immunohistochemistry performed in rat and bovine tissues established that chromogranin B is present in all cells of the adrenal medulla. It is also found in the anterior hypophysis, the endocrine pancreas, in enterochromaffin and in sympathetic ganglion cells, but e.g. is absent from posterior hypophysis and exocrine tissues. It is concluded that chromogranins A and B have a widespread distribution in endocrine and nervous tissue. Proteolytic processing of chromogranin B in the storage organelles of hypophysis and splenic nerves is apparently slower than that in chromaffin granules. The widespread distribution of the chromogranins resembling that of neuropeptides is a clear indication for some special, yet to be discovered, function.