Analysis of liver tissue for olestra following long-term feeding to rats and monkeys

The potential for olestra to be absorbed and to accumulate in tissues was investigated by analysing liver tissue from rats and monkeys in long-term feeding studies using sensitive chromatographic methods. Studies with intravenously administered olestra indicated that absorbed olestra is predominantly taken up by the liver. In monkeys, 74% of the injected dose was detected in the liver, as intact olestra, 48 hr after dosing. In rats, 58-96% of the injected dose was found in the liver, as intact olestra, within 24 hr. No olestra was detected (limit, 34 micrograms/g) in the livers of 14 monkeys fed olestra at 8% of the diet for 29 months. Also, no olestra was found in samples of liver, heart, kidney, spleen, lymph nodes and adipose tissues from 26 monkeys fed olestra at 0, 2, 4 or 6% of the diet, in random order, for consecutive 2-month periods. No olestra was detected in the livers of 47 out of 50 rats fed olestra at levels of up to 9% of the diet for up to 2 years. The amounts (2-4 micrograms/g) detected in the other three rats were near the detection limit of the chromatographic method (1.6 micrograms/g). The results show that accumulation of olestra in the liver, the primary target organ for absorbed olestra, was less than 3 x 10(-6)% of the total amount eaten by rats over 24 months and less than 4 x 10(-5)% of the amount eaten by monkeys over 29 months. These results are consistent with previous studies which showed that olestra is essentially not absorbed from the gastro-intestinal tract.