Oxalate absorption from intestinal segments of rats.

An animal experimental model was used to study oxalate absorption from the gut. It was found that the initial rate of [14C]oxalate absorption is rapid (6.5 per cent per min), and that after 5 min the rate of absorption decreases to about 0.6 per cent per min. Absorption of [14C]oxalate was greatest in the jejunum and least in the colon. On the basis of linear coefficients derived from the data, it is estimated that at least 8.6 per cent of a challenge dose of oxalate should be absorbed from the small bowel during normal transit. The high absorption rate, compared with the normal absorption of oxalate, in this model is most likely attributable to the oxalate's being completely dissolved in the gut. Magnesium and calcium in the test solution did not cause large changes in the rate or amount of oxalate transfer in this experimental model.