Somatostatin depletion by cysteamine: mechanism and implication for duodenal ulceration.

Cysteamine (CSH) and its close derivatives deplete immunoreactive somatostatin (SS) in rat organs. The effect of CSH is dose and time dependent and reversible. Structural requirements of the analogs are the presence of either -SH or -NH2 on a two- or three-carbon alkyl molecule; both radicals together increase, whereas insertion of carboxyl abolishes potency. The duodenal ulcerogenic potency of CSH derivatives is correlated significantly with their SS-depleting activity in the gastric mucosa. The mechanism of this action of CSH is poorly understood, but it is not caused by increased release, enhanced degradation of the peptide, or selective necrosis of SS cells. It is likely that in the intracellular environment CSH causes a conformational change in the peptide that affects the antigenic and functional properties of SS.