Biological and immunological properties of human gastrin I analogues.

The 15-methionine of human little gastrin I, prone to oxidation with concomitant loss of biological activity, has been replaced by leucine, norleucine and methoxinine, respectively. The resulting analogues exhibit acid secretory potencies practically undistinguishable from that of the parent hormone, whereas their immunoreactivity, as assayed with four different antisera raised against human little gastrin I, reflect to a significant extent the afforded modifications. Only [15-methoxinine]human little gastrin I retains practically the full reactivity for all antisera examined. The results suggest that this 15-methoxinine analogue is well suited for both biological and immunological studies.