Effects of plasma ochratoxin A and luminal pH on the jejunal absorption of ochratoxin A in rats.

The effects of iv injection of ochratoxin A (OA) on its absorption from the jejunum in rats were studied in vivo to demonstrate the jejunal absorption of OA in relation to the OA level in blood plasma. In addition the effects of the pH of the medium on OA uptake by the everted jejunum of the rat were studied in vitro to assess the contribution made by transfer of the non-ionized form of OA to the jejunal absorption of the toxin. The in vivo study showed that OA was absorbed from the jejunum even when its level was higher in the plasma than in the jejunal lumen. Jejunal uptake of OA in vitro was increased with a decrease in medium pH, the increase in uptake coinciding with an increase in the proportion of OA present in the non-ionized form. These results suggest that OA absorption is attributable mainly to transfer of the non-ionized form, and that a concentration gradient of the non-ionized form from the jejunal lumen to the blood and lymph may be achieved even when the total OA level is higher in the blood plasma than in the lumen.