Long-term distribution and metabolism of [1-14C]dolichol injected intravenously into rats

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Abstract
We have previously shown that [1-14C]dolichol mixed in vitro with rat serum and injected intravenously is rapidly cleared from the circulation and appears primarily in the liver. One day after injection the liver accounted for 80% of the isotope in whole animals, whereas after 130 days it represented only 50%. During the 130 days the specific radioactivity (dpm/g liver) decreased by more than 20-fold. In contrast, the spleen retained at 130 days 85% of the radioactivity initially present and its specific radioactivity decreased by only a factor of two. At this time small amounts of isotope were also found in carcass (internal organs removed), gastrointestinal tract and contents, and lungs. Trace amounts of radioactivity were extractable from testes and kidneys, while the heart and brain were essentially free of radioactivity. At all times after injection nearly all the radioactivity present in all tissues was still associated with dolichol. Only trace amounts of [1-14C]dolichyl fatty acyl ester and no [1-14C]phosphorylated derivatives of dolichol were present in the liver and spleen removed 156 days postinjection. Fractionation of liver between 1 h and 93 days after injection suggested that [1-14C]dolichol becomes associated primarily with a lysosome-enriched fraction. The accumulation of [1-14C]dolichol in this and other subcellular compartments involved both an inward and outward flow of radioactivity, suggesting that deposition of dolichol in lysosomes is not a one-way terminal process.