Effect of Nin-formylation of the tryptophan residue on gastrin (HG-13) binding and on gastric acid secretion.

The biologically active iodinated [Leu11]human gastrin-13 was found to exhibit high affinity for gastric mucosal cell receptors. We compared its biological activity on rat stomach and its receptor affinity on rat gastric mucosal cells isolated with pronase with those of a reversibly modified derivative obtained by direct Nin-formulation of the Trp10 residue. The results strongly suggested the involvement of the indole-NH group in both the specific binding of gastrin and the triggering of acid secretion.