Metabolism of a Plant Wax Paraffin (n-Nonacosane) in the Rat

Abstract

Utilization of orally administered long-chain solid paraffin hydrocarbons by the rat was studied with ¹⁴C-n-nonacosane (C₂₉ H₆₀) as a tracer and evidence was presented which shows that these wax hydrocarbons from food are absorbed and metabolized by the rat. Nonacosane, the major paraffin of most plant waxes, is partly absorbed from the digestive tract, the major portion (75%) being excreted. Of the administered radioactivity, 4% appeared in respiratory CO₂ during the 5-day experimental period. Radioactivity was widely distributed in the many tissues and organs examined, the liver having the greatest amount (about 2% of the administered ¹⁴C). Fractionation of total lipids from organs such as lung, heart, kidney and liver showed that paraffins accounted for less than 10% of the radioactivity. Gas-liquid chromatography of liver paraffins showed the presence of ¹⁴C-nonacosane. About 20% of the radioactivity in the blood was found in the paraffins. Although ¹⁴C was found in all classes of lipids in the liver, the major part of the radioactivity was in the phospholipids, almost all being in the fatty acid portion. Gas-liquid chromatography of the fatty acids derived from both the glycerides and phospholipids showed that most of the radioactivity present was present as C₁₅, C₁₆, C₁₇, C₁₈ and C₁₉ saturated fatty acids, the C₁₇ being the most radioactive.