Transport of [14C]coenzyme Q10 from the liver to other tissues after intravenous administration to guinea pigs.

After intravenous injection of [14C]coenzyme Q10 into guinea pigs, the blood level of radioactivity declined rapidly within 30 min. However, radioactivity in the blood subsequently increased, reached a peak at 8 h after the injection and thereafter decreased slowly. Since the liver uptake of radioactivity at 30 min after the injection was 87.8% of the dose and the increase of blood level was also seen in guinea pigs with bile duct fistula, it was concluded that the radioactivity taken up by the liver was redistributed to the blood and then transferred to other tissues. Tissue radioactivity levels were highest in the liver and spleen at 30 min after the injection and decreased thereafter. The levels in the blood and kidney peaked at 8 h, while those in the heart and brain peaked at 24 h and subsequently decreased. In contrast, the level in the adrenal gland was still increasing at 168 h after the injection; it rose sharply from 30 min, and at 24 h was higher than the level in any other tissue. Electrophoretic analysis showed that the radioactivity in serum at 8 h after the injection was associated with lipoproteins. It was confirmed by thin layer radiochromatography that the radioactivities in serum and liver at various times were due to coenzyme Q10 and coenzyme Q10 hydroquinone.