Measurement of secretin in the mucosa of digestive tract by radioimmunoassay.

Radioimmunoassay for measurement of mucosal secretin revealed that HCl was more efficient than distilled water for the extraction of secretin from canine duodenal mucosa. The rapid degradation of secretin within untreated mucosal specimens observed at room temperature could be effectively prevented by the storage at 4 degree C. In dogs, immunoreactive secretin distributed most abundantly in the upper and middle portion of the duodenum with a tendency to decrease gradually to the anal side. Secretin was not detected, however, in the esophagus, stomach, lower ileum, colon, liver and pancreas. The effect of intraduodenally instilled 0.1 N HCl on plasma and mucosal secretin was also investigated in conscious dogs. Plasma secretin rose promptly after the start of infusion and reached the maximum at 10 min, while mucosal secretin responded later than plasma secretin.