Evaluation of chromic oxide, glycerol triether, and β‐sitosterol as fecal flow markers in two species of nonhuman primates

Recovery of β‐sitosterol, glycerol triether (1‐hexadecyl‐2,3,‐didodecyl glycerol triether), and chromic oxide was studied in African green monkeys and stumptail macaques consuming diets containing 0.75 mg/Cal cholesterol and 38% of calories as safflower oil or butter. Following oral administration of these compounds, feces were collected daily for 9 days. For all animals, excretion of β‐sitosterol and glycerol triether paralleled one another almost exactly. Except for two animlas, this was also true for chromic acid. Essentially 100% of the administered β‐sitosterol and 90–95% of the glycerol triether were recovered; excretion of these markers virtually was complete by day 3. Ninety‐two percent of the β‐sitosterol was isolated in the nonsaponifiable lipid extract of the feces with less than 6% in the remaining aqueous phase. A maximum of 3.1% of the β‐sitosterol and 1.8% of the glycerol triether were found in the blood. For stumptail macaques, the major excretory form of β‐sitosterol was the 5β‐derivative. African green monkeys were more variable; one animal excreted the bulk of the β‐sitosterol unchanged while others excreted greater than 80% as the ring‐saturated 5β‐derivative. Animals consuming the safflower oil containing diet consistently excreted a greater percentage of the β‐sitosterol unchanged, compared with those animals eating the butter containing diet. There was no evidence for steroid ring degradation in any of the animals used in this study.