MORPHOLOGICAL-CHARACTERISTICS OF NATURALLY-OCCURRING ATHEROSCLEROSIS IN THE BRACHIOCEPHALIC ARTERY OF THE PIGEON

Endothelial characteristics and the macrophage foam cell nature of early naturally occurring lesions in the aorta and coronaries of the pigeon have been well characterized. However, the characteristics of pigeon atherosclerosis at other vascular sites have not been extensively studied. The present study was designed to compare atherosclerosis in the brachiocephalic artery with that in the coronaries and aorta. Forty-six White Carneau (WC) pigeons (26 female, 20 male) ranging in age from 2.5 to 7 years were necropsied after fixation under deep anesthesia by perfusion at 160 mm Hg with buffered glutaraldehyde. Arteries stained with Sudan IV for gross evaluation were subsequently processed for SEM and TEM. The occurrence of sudanophilia in the proximal brachiocephalic artery was greater in females ( 22 26) than in males ( 2 20). The endothelium, as studied by SEM, was intact over all normal and sudanophilic areas. Cell morphology varied with location in the vessel and gradually changed from polygonally shaped cells with prominent margins and protruding nuclei in the proximal brachiocephalic artery to elongated, flattened cells in distal regions. These regional differences were consistently observed, and did not correlate with age, gender, or areas of lipid accumulation. Unlike lesions in the coronary arteries and at the celiac bifurcation of the aorta, a relative paucity of white blood cells over diffuse sudanophilic areas was observed. This lack of adherent monocytes correlated with lesion ultrastructure. Connective tissue in the intima of the sudanophilic brachiocephalic arteries was disorganized, reflecting both an increase in matrix components and the presence of massive pools of extracellular lipid. Intracellular lipid was minimal and when present was confined to random droplets in the cytoplasm of intimal smooth muscle cells. Monocyte-derived foam cells, characteristic to other vascular beds, were absent from the brachiocephalic artery lesions. These results document differential lesion composition in the WC pigeons and suggest a gender-related susceptibility for brachiocephalic artery atherosclerosis in pigeons. © 1991.