Coronary arteriosclerosis in dogfish (Scyliorhinus canicula). An assessment of some potential risk factors.

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Abstract
Coronary myointimal lesions are described in the dogfish (Scyliorhinus canicula). These lesions are similar to those previously described in salmonids and are characterized by breaks in and disappearance of the inner elastic layer and intimal thickening as a result of inclusions of fibers and smooth muscle cells. Lesions are associated with all the branching points in the main subepicardial conal coronary arteries that supply the heart. Intimal thickenings were rare in other parts of these arteries. However, we found extensive lesions unassociated with branching points in two main intramyocardial ventricular arteries that supply the ventricular spongy myocardium. We carried out a statistical study of the incidence and severity of these intramyocardial lesions in relation to several potential risk factors. Intimal thickenings were present in 90.5% of the fish specimens and 40% of the histological sections. Sex, reproductive stage, plasma triacylglycerol, and cholesterol (total and related to high-density lipoproteins) were not significantly related to either the incidence or severity of lesions. Total fish length was significantly correlated with the lesion severity index (r = 0.33, p < 0.01). We also found significant differences in incidence related to the location of lesions. The middle areas of the intramyocardial branches, very close to the atrioventricular canal, were more affected than the cranial and caudal areas. The dorsal and ventral artery walls were also more affected than the lateral ones. The preferential location of the lesions in areas presumably subjected to mechanical stress because of a bifurcating bloodstream or the pulsatile flow throughout the atrioventricular canal suggests that coronary arteriosclerosis in dogfish is an age-related process, with hemodynamic factors playing a primary or secondary pathogenetic role. This disease seems not to be related to some factors suggested for salmonids, such as reproductive cycle, anadromous migration, river pollution, or plasma lipid concentration.