Complete tyrosine-O-sulphation of gastrin in neonatal rat pancreas.

Modification of tyrosine residues of proteins has attracted great interest. Although phosphorylation has received most attention, tyrosine-O-sulphation is also common and has been closely investigated in the hormones gastrin and cholecystokinin (CCK). CCK regulates pancreatic enzyme secretion. It is always sulphated and sulphation increases its pancreatic secretagogue activity 100-fold. By contrast, only half of gastrin molecules are tyrosine-O-sulphated and sulphation does not influence the ability of gastrin to regulate gastric acid secretion. We now report that in neonatal rat pancreas, which is the major source of gastrin in the newborn rat, gastrin is completely sulphated. Moreover, the disappearance of gastrin from the pancreas during the first weeks after birth parallels the appearance of CCK in the intestine. Since sulphation is essential for pancreatic secretagogue activity of gastrin as well as of CCK, pancreatic gastrin in the neonate may be the equivalent of intestinal CCK in the adult.