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

Abstract

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, CCl₄) 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, 10and 20 min after the addition of 25, 50 or 200μl CCl₄ in the central well. 50 ml of a 6 mg/ml liver cell suspension were poured in a 120 cm² Petri dish and the sediment liver cell monolayer was exposed to UV Bradiation 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 CCl₄ 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.