Reevaluation of regression of coronary arteriosclerotic lesions in repeat-spawning steelhead trout.

At spawning, migratory salmonids have an extensive accumulation of coronary arteriosclerotic lesions. Nevertheless, when steelhead trout (Oncorhynchus mykiss) return to the ocean after spawning, an unusual phenomenon has been reported, namely, that these lesions have regressed naturally and almost completely (R.L. Van Citters and N.W. Watson, Science 1968; 159:105-107). In contrast to this earlier finding, we present data that show a high prevalence and severity of coronary lesions in 1) wild, repeat-spawning steelhead trout that were caught at high sea and 2) wild and cultured steelhead trout that had been held in sea pens for up to 1 year after maturation. Therefore, we refute the idea of natural lesion regression in steelhead trout. Coronary lesions in salmonids are characteristically lipid free despite the fact that there are high plasma levels of both total cholesterol and low density lipoproteins. This situation contrasts with the characteristic lipid deposition during lesion development in mammals. We therefore suggest that attention should be directed to explaining why coronary lesions accumulate despite very high dietary levels of omega-3 polyunsaturated fatty acids in the diets and tissues of these fish.