Coronary myointimal hyperplasia in freshwater Lake Michigan salmon (genus Oncorhynchus). Evidence for lipoprotein-related atherosclerosis.

The relationship between plasma lipoprotein concentration and histologic myointimal proliferative lesions in the coronary vessels was examined in 37 freshwater Chinook salmon (Oncorhynchus tshawytscha). The fish were obtained during the migrating, schooling, and spawning periods of the fourth year of life. Plasma apoB polypeptides were maximally elevated in the migrating fish in correlation with a high degree of coronary vascular disease. Both the relative incidence and the severity of lesions were greater in migrating salmon as compared with spawning fish. In contrast, plasma apoA polypeptides were maximally elevated in association with reduced levels of plasma apoB in spawning fish in which coronary lesions were reduced in severity and incidence. Simultaneous observations confirmed the relative decrease in circulating thyroid hormone and increase in adrenal cortical hormones characteristic of the maturation process. These data in the mature freshwater Lake Michigan Chinook salmon provide direct support for the hypothesis that coronary proliferative atherogenesis proceeds in parallel with excessive exposure to apoB-containing lipoproteins and that reversal is associated with excessive exposure to apoA-containing lipoproteins. The temporal relationship to altered hormone status is described, but the pathophysiologic significance for atherogenesis cannot be determined from these data.