[Demonstration of specific receptors for gastric inhibitory peptide (GIP)]

Receptors for the Gastric Inhibitory Polypeptide (GIP) were characterized in particles enriched in plasma membranes obtained from a transplantable hamster insulinoma. Native GIP, at concentrations between 10(-10) and 10(-6) M, inhibited competitively the binding of 125I-GIP to membranes. The binding was highly specific since, among the peptides tested, only the porcine peptide having N-terminal histidine and C-terminal isoleucine amide (PHI), at high concentration (10(-6) M), inhibited by 17% the binding of 125I-GIP. The existence of these receptors suggested that GIP could act directly on beta-cells.