Development of region-specific radioimmunoassays against rat prosecretin or secretin and their characterization

We have raised four region-specific antisera in rabbits against rat prosecr etin or secretin using synthetic peptides such as prosecretin(1-41), prosec retin(1-11), prosecretin(98-113) and secretin and developed three region-sp ecific radioimmunoassays (RIAs) for prosecretin(1-41), prosecrtin(1-11) and secretin. The results showed clearly the presence of prosecretin-like pept ides in rat gastrointestine, whereas only a trace of prosecretin-like IR we re recognized, if any, in the brain. In the Wistar male rat gastrointestine , the highest concentration of both prosecretin(1-41)-like and secretin-lik e immunoreactivity (IR) were detected in the ileum rather than in the duode num, It is noteworthy that serial section of rat deodenum revealed the posi tive staining of prosecretin(98-113)-like IR in the cells identical to thos e stained with both anti-prosecretin(1-41) serum and anti-secretin serum. T hese result, clearly indicate the presence of the C-terminal fragments of p rosecretin as the processing products. In contrast, anti-prosecretin(1-11) serum did not recognize the immunoreactivity in any of the cells in the bra in and gastrointestine.