Somatostatin

The discovery of hypothalamic factors that inhibited growth hormone secretion and of pancreatic factors that inhibited insulin secretion were the first clues to the existence of somatostatin. During the course of efforts to isolate growth hormone releasing factor, Krulich, McCann and Dhariwal found that hypothalamic extracts contained a potent inhibitor of growth hormone secretion. They postulated that growth hormone secretion was under a dual control system, one inhibitory and the other excitatory (I) . In studies being carried out at about the same time, Hellman and Lernmark found a factor in pancreatic extracts that inhibited insulin secretion (2). They postulated that islet cell function was regulated by local hormonal factors. With the isolation and chemical characterization of somatostatin by Brazeau and colleagues (3), and the availability of relatively large amounts of the synthetic peptide for research, it has been possible to demonstrate that both predictions were true. Subsequent work revealed that somatostatin, as initially isolated (somatostatin 14), was but one of several related peptides, part of a multigene family, with tissue specific processing. Many of the details of biosynthesis and genetic control have been worked out, and this molecule has served many workers as a model gut-brain peptide for detailed study. The peptides are widely distributed in tissues and exert an extraordinary range of effects on most glandular secretions, both internal and external.