The effect of carbon tetrachloride and ultraviolet radiation on dolichol levels in liver cells isolated from 3- and 24-month-old male Sprague-Dawley rats

Dolichol (D) is a long-chain polyprenoid broadly distributed in the cell membranes, possibly endowed with a free-radical scavenging activity, whose concentration in tissues increases with increasing age. No enzyme pathway for D degradation has been discovered. In order to test the hypothesis that D might undergo a non-enzymatic free-radical mediated decomposition the effects of a xenobiotic agent (carbon tetrachloride, CCl(4)) and ultraviolet-B (UV-B) radiation on D levels were studied in liver cells isolated from male ad libitum fed Sprague-Dawley rats aged 3 or 24 months. Liver cells (90 mg/ml) were incubated in sealed flasks (6 ml cell suspension each) for 0, 5, 10 and 20 min after the addition of 25, 50 or 200 microl CCl(4) in the central well. 50 ml of a 6 mg/ml liver cell suspension were poured in a 120 cm(2) Petri dish and the sediment liver cell monolayer was exposed to UVB radiation for 0, 5, 10, 20 and 40 min. At the given time, cells were taken and D was extracted and assayed by the HPLC procedure. D levels were remarkably higher in older than in younger cells as expected ( P < 0.001). Treatment with CCl(4) and UVB caused a highly significant decrease in D ( P < 0.001) whose percentage was larger in younger than in older cells. The conclusions are that free-radicals generated either by chemical or by physical agents cause a very rapid depletion of D in liver cells, and that the effect of the free radical attack on D decomposition may be lower percentage wise in older than in younger cells, which might account at least in part for the accumulation of D in older tissues.