LIPID ABNORMALITIES IN RATS GIVEN SMALL DOSES OF LEAD

Previous human and experimental studies have demonstrated that lead ex posure may modify the metabolism of lipids. Several studies have indic ated that exposure to lead produces an increase in lipid peroxidation and inhibits blood superoxide dismutase activity. Recently, lipid pero xides have been shown to impair tissue membranes and to be a risk fact or for vascular diseases. The aim of the present investigation was to evaluate the impact of subclinical lead poisoning on rat lipids in the context of atherosclerosis. The degree of poisoning was analogous to that in populations exposed to lead in a contaminated environment. Exp eriments were performed on male Buffalo rats with body weights of 150- 200 g. The experimental animals received lead acetate intragastrically in doses of 35 mg lead/kg body wt. (Pb/kg) once weekly or 70 mg Pb/kg twice weekly for 7 weeks. Control rats were fed in the same manner wi th sodium acetate equimolar to the acetate in the lead acetate solutio n. One day after the feeding was over, venous blood samples, under eth er anesthesia, were collected. The animals were killed by exsanguinati on and the liver was excised for determination of the metal (lead, cop per, and zinc) content. A segment of the abdominal aorta was excised f or histological examination. In venous blood the following were estima ted: triglycerides, total cholesterol, high-density lipoprotein (HDL)- cholesterol fraction, serum lipid peroxides, and blood superoxide dism utase activity. Metal content (lead, copper, and zinc) in blood and li ver was determined by means of atomic absorption spectrophotometry. In rats poisoned with small doses of lead, decreases in the plasma chole sterol level and the HDL-cholesterol fraction were observed. In parall el with the decrease in the cholesterol concentration, lead increases the serum triglyceride level, this increase being dependent upon lead levels in blood. In our studies a significant influence of lead on ser um lipid peroxide level or blood superoxide dismutase activity was not found. In the histological examination, atrophy of the elastic fibers in the aorta was observed. The possible significance of the inhibitor y effect of lead on lipoprotein lipase activity is discussed.