Rats fed on atherogenic diets containing 2% cholesterol and 0.5% cholic acid with or without 0.15% thiouracil were exposed to carbon disulphide (CS2) vapours (1 mg/l of air), five hours a day, six days a week for 6-10 months. Serum and aorta lipid contents were determined, and the extent of atherosclerotic changes was investigated. The following effects of chronic exposure to CS2 were found: (1) slower gain in body weight when rats were fed on atherogenic diet; (2) greater increase in serum cholesterol content (after thiouracil supplemented diet); (3) moderate increase in total cholesterol content in the aorta wall with a significantly increased esterified cholesterol fraction but none in phospholipid level in this tissue; and (4) more advanced lipid infiltrates of coronary arteries and endocardium, the latter predominantly in the aortic valves. These results together with data from previous studies indicate that metabolism of arterial lipids participates in the process of artheroma formation after chronic exposure to CS2 vapours.

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1. The normal lipolytic activity (LA) of rat aorta shows considerable individual, age, and sex differences. 2. LA was determined by release of non-esterified fatty acids (NEFA) from lipaemic human serum. 3. Addition of eserine in concentrations inhibitory only to cholinesterases results in approximately 50 % inhibition of LA. 4. Low concentrations of tetra isopropylpyrophosphoramide (iso-OMPA) produced a mean inhibition of 93 %. Up to 100 % inhibition occurred in individual cases. 5. These results suggest that at least 50 % LA of rat aorta depends on non-specific cholinesterase (ChE) and the remainder possibly on an eserine-resistant, iso-OMPA- sensitive aliesterase. 6. Administration of iso-OMPA to living animals produced a fall in plasma NEFA and a reduced aortic LA (to 30 % of normal). ChE activity in cold microtome sections of aorta was completely inhibited. 7. Since no clinical or morphological changes could be observed in the iso-OMPA treated animals, its long term administration is apparently perfectly feasible.