The response of rat serum lipids to diets of varying composition or contaminated with organochlorine pesticides.

The effects of different diets (high carbohydrate, high protein, high fat) and diets contaminated with polychlorinated biphenyls (PCBs) and/or gamma-hexachlorocyclohexane (lindane) on the levels of serum triglycerides, cholesterol and phospholipids were investigated in Wistar rats. Serum triglyceride levels differed significantly among the diets, while those of cholesterol and phospholipids were much less affected by the diet composition. A change in diet composition resulted in a gradual adaptation to the lipid levels characteristic of the new diet with major variations including oscillations. There was, however, no specific component of a diet that could be associated with any specific change in serum lipids. While feed deprivation decreased the serum lipids (40-65% in 3 days), refeeding the starved animals caused pronounced increases of the lipids that were different among the diets. The response of the triglyceride levels was the strongest (up to 10 times the starvation levels) followed by those of the phospholipids (4-fold) and cholesterol (2.5-fold). Response of the triglyceride levels peaked within 1 or 2 days of refeeding, whereas those of cholesterol and phospholipids took 4 days to reach the maximum. Feeding PCB-contaminated diets increased the serum lipids in a dose-dependent manner (15-250 ppm). Higher PCB concentrations were increasingly inhibitory (350 ppm) or overtly toxic (> 400 ppm). Elevated lipids returned to the starting levels immediately after peaking (triglycerides) or only after several days (cholesterol, phospholipids) but with an earlier onset at lower PCB concentrations. Refeeding starved animals with PCB-contaminated diets also increased the serum lipids dose-dependently. Feeding lindane-containing diets (50-150 ppm) as well as refeeding animals with lindane diets resulted in a considerable increase of the triglyceride levels, while cholesterol and phospholipids increased much less. Higher lindane concentrations (250 ppm) were inhibitory. The outcome on serum lipid levels on feeding diets contaminated with both PCBs and lindane was basically additive.