Influence of calcium on aluminum accumulation by the rat jejunal slice.

The isolated rat jejunal slice was used to determine if aluminum (Al) interacts with the gastrointestinal (GI) calcium (Ca) transporting system. Al uptake by the rat jejunal slice was reduced by Ca channel blockers (verapamil, nifedipine, diltiazem-10 microM) and a medium containing no added Ca. Conversely, Al uptake was increased by Ca channel activators (4-aminopyridine, .05mM, .1mM; Bay k 8644, 1, 10 microM) and by 5mM Ca. Al uptake was saturable and energy dependent but yielded a low activation energy (Ea = 3.9 +/- 0.3 kcal/mole). Al uptake was increased by vanadate (100 microM), an inhibitor of both the active Ca pump and Na/K-ATPase. These results suggest that Al does interact with the GI Ca transporting system. This interaction may form the basis for its accumulation and toxicity in different tissues which contain similar processes for handling Ca.