Sterol metabolism. 2. The absorption and metabolism of [14C]ergosterol in the guinea pig

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Abstract
The absorption by young female guinea pigs of ergosterol and of uniformly C14 -labeled material dispersed in ethyl oleate was shown to be small but significant. Similarly, absorption of the latter dispersion by male guinea pigs is also poor, but that of a suspension of C-14 ergosterol in aqeous Tween 80 is a little better. A possible reason for the poor absorption is discussed. The percentage absorbed was less than 0.3% estimated spectroscopically, and 0.6-4.8% by the assay of C14 in lipid fractions of the liver, intestine and adrenals. The discrepancy in the 2 values obtained by the different methods arises from the active metabolism of the ingested ergosterol. Moreover, the small amounts of radiocarbon which would normally enter the protein fractions from the labeled intermediary metabolites were not assayed. The main immediate metabolic products of ergosterol found in the intestine, liver and adrenals are acidic in nature. Some of these, however, may arise by oxidative attack in the intestine. The uptake of radioactivity by the adrenals 17 hours after dosing was as high as that by the liver, indicating that adrenals play an important role in the metabolism of dietary ergosterol.