Nickel absorption from perfused rat jejunal and ileal segments.

The intestinal absorption of Ni2+ was studied in isolated perfused jejunal and ileal segments of rats, by a method which allows continuous sampling of the absorbates. The results showed that the Ni(2+)-absorption proceeds at a much higher rate in the jejunum than in the ileum. Several observations indicate that Ni2+ is absorbed actively in the jejunum. There are indications in the literature that Ni2+ at least partly may share the transport mechanism for iron across the intestinal mucosa and our results may reflect the participation of Ni2+ in this absorptive process. The transfer of Ni2+ across the ileal epithelium may occur by passive diffusion. Addition of Zn2+, Co2+, Cd2+ or Hg2+ to the jejunal perfusates affected the Ni(2+)-absorption to varying extents. Thus, Zn2+ had minor effects on the Ni(2+)-absorption. Co2+ decreased the Ni(2+)-concentration in the absorbates, possibly by interfering with Ni2+ in the iron transfer process. Addition of Cd2+ or Hg2+ to the perfusates resulted in decreased jejunal water absorption. Hg2+ also depressed the glucose absorption. These results show that Cd2+ and Hg2+ at low concentrations are toxic to the jejunal mucosal cells. Thus, these metals can inhibit the amount of Ni2+ transferred across the intestinal mucosa by decreasing the volume of the absorbate.