Effect of (Asu1,7)-EEL calcitonin and its fragments on gastric acid secretion in rats.

Effect of [Asu1, 7]-eel calcitonin ([Asu1, 7]-E-CT), an analogue of natural eel calcitonin, and its fragments on gastric acid secretion was studied in pylorus-ligated rats. [Asu1, 7]-E-CT markedly reduced the acid secretion with intravenous and intramuscular doses of 3 Medical Research Council units (MRC U)/kg or 0.6 μg/kg. This activity was comparable to that of salmon calcitonin and porcine calcitonin compared with equivalent hypocalcemic doses and was consistently evident during daily administrations for 10 days. Assay of six fragments of [Asu1, 7]-E-CT showed that the C-terminal peptide consisting of 22 amino acids diminished the acid secretion but shorter peptides of the C-terminal fragment or the Nterminal fragments did not. These results suggest that the C-terminal peptide may play an important role in this action of [Asu1, 7]-E-CT, and a peptide chain of over 18 amino acids is required.