The tissue and subcellular distribution of [3H]dolichol in the rat

Following the intravenous injection of nanomolar amounts of ³H]dolichol into rats, the radioactivity rapidly appeared in the high-density lipoprotein fraction of the plasma and circulated with a half-life of about 9 h. A fraction of the injected activity was excreted in the feces, presumably through the bile, but evidence was obtained that little oxidative breakdown of dolichol occurred. All tissues assayed acquired radioactivity, but the liver attained the highest specific activity and the largest percentage of the total radioactive dolichol. Subcellular fractionation of the liver revealed that mitochondrial preparations contained the bulk of the labeled dolichol at all times tested up to 40 h after injection. Disruption of the mitochondrial structure by two different techniques permitted the isolation of inner and outer membrane fractions and it was found that the ³H]dolichol was concentrated in the outer membrane fraction. The significance of these findings is discussed.