NICKEL ABSORPTION FROM PERFUSED RAT JEJUNAL AND ILEAL SEGMENTS

The intestinal absorption of Ni2+ was studied in isolated perfused jej unal and ileal segments of rats, by a method which allows continuous s ampling of the absorbates. The results showed that the Ni2+-absorption proceeds al a much higher rate in the jejunum than in the ileum. Seve ral observations indicate that Ni2+ is absorbed actively in the jejunu m. There are indications in the literature that Ni2+ at least partly m ay share the transport mechanism for iron across the intestinal mucosa and our results may reflect the participation of Ni2+ in this absorpt ive process. The transfer of Ni2+ across the ileal epithelium may occu r by passive diffusion. Addition of Zn2+, Co2+, Cd2+ or H2+ to the jej unal perfusates affected the Ni2+-absorption to varying extents. Thus, Zn2+ had minor effects on the Ni2+-absorption. Co2+ decreased the Ni2 +-concentration in the absorbates, possibly by interfering with Ni2+ i n the iron transfer process. Addition of Cd2+ or Hg2+ to the perfusate s resulted in decreased jejunal water absorption. Hg2+ also depressed the glucose absorption. These results show that Cd2+ and Hg2+ at low c oncentrations are toxic to the jejunal mucosal cells. Thus, these meta ls can inhibit the amount of Ni2+ transferred across the intestinal mu cosa by decreasing the volume of the absorbate.