Abstract
Summary
A study was undertaken to relate the magnitude of the cholesterol-esterifying activity in aortic microsomes to the susceptibility of species to atherosclerosis and to the propensity of the thoracic and abdominal segments within a species to develop atherosclerosis. The cholesterol-esterifying activity was the greatest in the rat, probably the most resistant to atherosclerosis, and the least in the cockerel, one of the species more susceptible to atherosclerosis. The cholesterol-esterifying activity in the aorta was the same for the dog (atherosclerosis resistant) and the rabbit (atherosclerosis susceptible). Relative cholesterol-esterifying activities of thoracic and abdominal portions of the aorta within a species also did not coincide with the relative susceptibility of these anatomical sites to atherosclerosis. The cholesterol-esterifying activity was examined in the aortas of two genetic strains of pigeons which vary in their susceptibility to atherosclerosis; the enzyme activity in the aorta of the White Carneau (atherosclerosis resistant) was the same as that of the Show Racer (atherosclerosis susceptible). Thus, cholesterol-esterifying activity does not consistently reflect the predisposition of the tissue to develop atherosclerosis.
Pigeon microsomes displayed an unexpected difference between the sexes. In the Show Racer, cholesterol-esterifying activity was significantly greater in the female aortic microsomes than in the male. A similar but smaller trend was apparent in the White Carneau.
We express our appreciation to Dr. T. B. Clarkson for the Show Racer and White Carneau pigeons and for his helpful suggestions concerning the treatment of these animals. We express our gratitude to Mrs. L. Berg for her expert laboratory assistance.
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