In vitro intestinal transport of vasopressin and its analogues

The intestinal transport of vasopressin and oxytocin and their analogues 1-deamino-8-D-arginine vasopressin and 1-deamino-2-tyrosine(omicron-ethyl)-oxytocin was studied in everted segments of rat jejunum. The transported peptides were identified by specific RIA methods and by quantitative high pressure liquid chromatography. Transport rates were highest for 1-deamino-8-D-arginine vasopressin and lowest for vasopressin. No transport maximum and no competitive inhibition could be demonstrated. The distribution volume of the peptides in the intestinal mucosa was found to be smaller than that of polyethylene glycol. It is concluded that peptides of this size are transferred across the intestinal mucosa by passive processes.