Quantitation of dolichyl phosphate and dolichol in major organs of the rat as a function of age

Previous studies in mice and humans have shown age-related increases in the levels of dolichol in all organs investigated. In the present study, the levels of dolichyl phosphate, the physiologically active form of dolichol, as well as dolichol and cholesterol were determined in five major organs of the rat from 4 to 14 wk of age. As observed for mice and humans, the levels of dolichol increased in all tissues examined, especially testis where an eightfold increase was found. Cholesterol levels remained relatively constant in all tissues examined except brain, where a threefold increase was observed. Hepatic dolichyl phosphate levels decreased slightly during growth while nonhepatic tissues showed moderate (1.2-1.7-fold) increases. It is proposed that steady-state levels of hepatic dolichyl phosphate are maintained in the face of constant de novo synthesis by a combination of two pathways: export, either via the circulation or the previously demonstrated fecal route (Connelly and Keller [1984] Bioscience Reports 4, 771-776) and conversion to dolichol with subsequent accumulation.