STUDIES OF TYRAMINE TRANSFER AND METABOLISM USING AN IN-VITRO INTESTINAL PREPARATION

The duodenal transfer and metabolism of [H-3]tyramine from sacs and pe rfused segments of rat intestine were determined. In sacs, a linear re lationship between the steady-state transfer rate of total tritium and the initial mucosal tyramine concentration was observed, suggesting t hat the clearance is the same at different concentrations. In duodenal perfusions, there was no significant difference in the amount of tota l tritium removed between control and everted tissues, whether the flo w was 0.2 or 2.0 mL/min. The percentage of [H-3]tyramine extracted fro m the gut lumen depended on the flow rate. About 30-40% of the extract ed drug was metabolized; this value decreased to 20% when the rats wer e pretreated with pargyline. The data support the idea that the transf er mechanism for tyramine is simple diffusion.