Secretin and insulin: response to intraduodenal acid.

Immunoreactive secretin (IRS) and immunoreactive insulin (IRI) levels were measured in humans and dogs following the intraduodenal instillation of hydrochloric acid. IRS levels rose after acid in both instances, but a concomitant rise in peripheral IRI levels was not noted. Premedication of the humans with Scopolamine prevented a rise of IRS in the human subjects. It is concluded that the endovenous release of IRS alone does not result in increased IRI levels in peripheral blood and that IRS release may be under vagal control.