SecretinのRadioimmunoassayとその臨床応用に関する研究

Abstract

Radioimmunoassay (RIA) for the determination of plasma secretin was investigated fundamentally and was clinically applied for the examination of secretin release in response to an intraduodenal acid infusion. The secretin RIA was finally established by use of anti-porcine secretin rabbit serum, 125(125うえ)I labelled 6-tyrosyl secretin as a tracer hormone, and Squibb's synthetic secretin as the standard hormone. We devised a way to the incubation of a two step method namely, preincubation and postincubation method, and to a single antibody method by means of polyethyleneglycol. The measurable lowest limit of this RIA was 100 pg/ml of secretin. In clinical investigations, basal plasma immunoreactive secretin levels before intraduodenal acidification in 13 out of 15 control patients were less than the measurable limit and the mean was 109 pg/ml when the value less than 100 pg/ml was used for tentative calculations as 100 pg/ml. However, the mean values calculated as before showed increases after intraduodenal acidification to 243.5 pg/ml at 5 minutes, 397.7 pg/ml after 10 minutes indicating the maximum, 217.3 pg/ml at 20 minutes, and 126.7 pg/ml at 30 minutes. In patients with chronic pancreatitis, the secretin level prior to acidification showed more than 100 pg/ml in 4 out of 5 cases with a mean of 180 pg/ml, while the secretin releasing responses to the acidification were remarkably lower than the control, and the responses were also impaired in case of diabetes mellitus showing intermediate levels between chronic pancreatitis and the control. On the other hand, the responses of secretin release to duodenal acidification in patients with duodenal ulcer were lower and the delay of appearance of the peak was noted. It was suggested from the above descrived results that the secretin release was also impaired in duodenal ulcer in spite of the hypersecretion of gastric acid.