Nickel Absorption from Perfused Rat Jejunal and Ileal Segments

Abstract

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.

Enhanced Intestinal Nickel, Absorption in Iron‐Deficient Rats

“…It is possible that the transfer system for iron may contribute to the jejunal absorption of nickel even in these rats. The nickel absorption in the ileum in normal rats may occur passively via the paracellular pathway (Tallkvist & Tjalve 1994). However, as shown in the present study, the ileal nickel absorption can be enhanced in iron-deficiency, apparently due to participation of the metal in the transfer system for iron.…”

“…The results of our previous study (Tallkvist & Tjalve 1994) have indicated that nickel may be transferred across the jejunal epithelium by an active transcellular pathway also in normal rats. It is possible that the transfer system for iron may contribute to the jejunal absorption of nickel even in these rats.…”

“…& 1990. It is probable that the transfer process involves an uptake through the intestinal epithelium followed by a passage via blood and lymph vessels in the lamina propria, into the absorbate (Tallkvist & Tjalve 1994). Thus, one can pre- sume that the transfer process requires a certain period of time.…”

“…We have recently examined the absorption of nickel in isolated perfused jejunal and ileal segments of rats (Tallkvist & Tjalve 1994). The results showed that nickel is absorbed at a much higher rate in the jejunum than in the ileum.…”

Essentiality of nickel and homeostatic mechanisms for its regulation in terrestrial organisms

“…In it, Ni is bound to various proteins, amino acids, and other molecules for distribution and sequestration in the body. The research of Tallkvist and Tjälve (1994) suggests that Ni is transported actively across the gut lumen, at least in the rat jejunum, perhaps sharing the Fe transport mechanism (Forth and Rummel 1973). Exogenous chelators, such as hydroxyquinoline (8-OH-quinoline) or 5-chloro-7-iodo-8-hydroxyquinoline (clioquinol), also increase Ni 2+ gastrointestinal absorption and influence tissue distribution (Borg-Neczak and Tjälve 1994).…”