Comparative studies on the hypercholesterolaemia induced by excess dietary tyrosine or polychlorinated biphenyls in rats.

1. The effects of dietary polychlorinated biphenyls (PCB) and excess tyrosine on serum and liver lipids, urinary ascorbic acid and catecholamines were compared in male Wistar rats. 2. Serum levels of cholesterol, urinary ascorbic acid, norepinephrine, epinephrine, dopamine and histamine were significantly increased in rats given either PCB or excess tyrosine. 3. The hypercholesterolaemia induced by PCB or excess tyrosine was blocked by the adrenergic alpha-blocker, phenoxybenzamine. 4. The present results suggest causal interrelations between the hypercholesterolaemia induced by dietary PCB or excess tyrosine and the secretion of catecholamines.