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In the present work the uptake and utilization of [14C]erucic acid by the perfused rat heart has been investigated and compared with those of [14C]-palmitic acid. Both fatty acids were found to be taken up by the heart at the same rate. On the other hand, the incorporation of erucic acid into tissue lipid during 30 min perfusion were significantly high and CO2 production low as compared with palmitic acid. Incorporation of erucic acid into diacylglycerol, triacylglycerol and cholesterol ester was considerably higher than that of palmitic acid. During a 30-min period, a large amount of [14C]erucic acid was accumulated in tissue fatty acid fraction. Similarly, relatively high labelling was found in the fatty acid and diacylglycerol fraction during the initial 300 s of perfusion with erucic acid. When [14C]erucic acid and unlabelled palmitic acid was used, the radioactivity was very high in the fatty acid fraction of the heart lipid in comparison with the experiment when [14C]palmitate and unlabelled erucic acid was used. Therefore, erucic acid is poorly oxidized by the heart and is preferentially incorporated into heart lipids. There was relatively high incorporation of [14C]erucic acid into diacylglycerol and addition of unlabelled palmitic acid tended to decrease it, probably converting more diacylglycerol to triacylglycerol. When [14C]palmitic acid and erucic acid were used together, incorporation to triacylglycerol was high and diacylglycerol low. These results, therefore suggest that palmitic acid is a more suitable acyl donor than erucic acid for the C-3 position of triacylglycerol, especially when the diacylglycerol contains erucoyl moieties.

Rats of weaning age were feed for a period of 1 or 3 weeks either a low fat diet (laboratory stock diet) or a semi-synthetic diet containing 20% by weight of either corn oil (2/3 of the total fatty acids consisted of linoleic acid) or mustard seed oil (1/3 of the total fatty acids were comprised of erucic acid). Feeding of a diet rich in erucic acid for 1 week increased by twofold the cholesterol ester content of the aorta. However, the concentrations of unesterified cholesterol and individual phospholipids in the aorta were uninfluenced by hyperlipemia induced by this diet. Fatty acid analyses indicated that erucic (22:1) and eicosenoic (20:1) acids are found in the triglyceride and cholesterol esters of the aorta in the proportion similar to that found in the plasma triglyceride and cholesterol esters. Our results demonstrated further that a significantly greater quantity of 14C-labelled erucate than labelled palmitate, oleate or linoleate was incorporated into the cholesterol ester fraction of the control aorta. The incorporation rates of erucate and linoleate into phosphatidic acid were more rapid, while the rates of erucate into phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol and lysophosphatidylcholine were significantly slower than those of other fatty acids.

When male weaning rats were fed a high fat-high erucic acid and diet (mustard seed oil) for 1 week, there were increases in the triglyceride and erucic acid contents in the myocardium, and an increase in the rate of incorporation of [1-14C]palmitic acid into triglyceride in the perfused heart, in comparison to rats that had consumed a high fat-high linoleic acid diet (corn oil) or a low fat diet (laboratory chow). However, continuation of the mustard seed oil diet (3-6 weeks) tended to normalize these biochemical parameters. The size of the papillary muscle isolated from the mustard seed oil-fed rats was greater than that of the muscle of the chow-fed rats, and its developed isometric tension was lower. Electron microscopic examination revealed that, in the hearts of rats having eaten the mustard seed oil diet, there were isolated foci where the number and size of mitochondria appeared to be increased.