Coronary arteriosclerosis in salmon: growing old or growing fast?

A review is presented of what we know and what we suspect regarding the formation of coronary arteriosclerotic lesions in salmonids. Coronary lesions are a fact of life for both Atlantic and Pacific species of migrating salmon. Severe forms of lesions, usually restricted to the main coronary artery, are typically found in the majority of a salmon population when they are spawning. Vascular injury to the coronary artery, as a result of the bulbus arteriosus being excessively distended, is proposed as an initiating mechanism for coronary lesion formation, possibly explaining why severe lesions are restricted primarily to the main coronary artery. Evidence is presented that coronary arteriosclerosis in salmonids develops in immature fish, well before maturation, and progresses with age. Growth and growth rate are implicated in lesion progression. A faster growth rate could produce a more stressful life style, which in turn initiates more coronary vascular injury. Dietary factors, especially polyunsaturated fatty acids (and their metabolites), can significantly stimulate vascular smooth muscle proliferation in the salmon coronary artery, but a possible linkage to the progression of coronary lesions has yet to be studied. Whether coronary lesions negatively impact blood flow to the salmon heart has not been properly studied. Nevertheless, the coronary blood supply to the heart has functional importance when salmon exercise and the coronary flow reserve may be reached when fish swim under mild hypoxic conditions. If coronary arterial lesions do adversely affect blood flow to the heart, the selective effects would be most prominent in years when upstream migration conditions are particularly severe.