Effects of clofibrate, phthalates and probucol on ubiquinone levels.

Rats were exposed through their diet to clofibrate, di(2-ethylhexyl)phthalate or probucol for 6 weeks and the levels of ubiquinone (UQ), cholesterol and dolichol were monitored in liver, muscle, heart, brain and blood. The levels of UQ-9 and -10 were increased by clofibrate and, in particular by phthalate administration. With the latter agent this increase in liver was fourfold, in muscle was twofold and levels in the heart and blood increased by 20%, whereas there was no change in the brain. Probucol led to a moderate decrease in the level of UQ in liver, muscle and blood, but not in heart or brain. The extent of reduction of UQ was not modified by any of the treatments employed. Probucol did not have any effect on tissue or blood cholesterol levels, whereas clofibrate or phthalate elicited a variable response, including both increases and decreases depending on the tissue analyzed. Phthalate treatment increased the dolichol content to some extent in all tissues and in blood, but the level of this lipid was not modified upon clofibrate or probucol treatment. These results demonstrate that tissue and blood levels of UQ can be increased by exposure to appropriate chemical agents without elevating the concentration of cholesterol.