Proline hydroxylase activity and collagen content of pigeon aortas with naturally-occurring and cholesterol-aggravated atherosclerosis.

Proline hydroxylase activity and collagen content were determined in atherosclerotic plaque, fatty streak, and normal tissue from aortas of White Carneau pigeons with naturally-occurring of cholesterol-aggravated atherosclerosis. Little increase in collagen content or proline hydroxylase activity occurred in fatty streaks or plaques from birds with cholesterol-aggravated atherosclerosis. This is consistent with the morphologic observation of the presence of little or no "fibromuscular cap" in these cholesterol-aggravated lesions. Both normal and plaque tissue from arotas of birds with naturally-occurring atherosclerosis contained more collagen than did similar tissues from control birds or birds with cholesterol-aggravated lesions. The largest proportion of this increase in collagen content probably represented an age effect since it occurred in normal as well as atherosclerotic tissue. Plaques from aortas of birds with naturally-occurring atherosclerosis did contain, however, significantly more collagen than normal tissue from the same aortas. This is consistent with the presence of a prominent "fibromuscular cap" in these naturally-occurring lesions. Proline hydroxylase activity was less in these lesions than in normal tissue from the same aortas. Consequently increased proline hydroxylase activity and collagen content are not greatly altered in association with development of cholesterol-aggravated atherosclerotic lesions in pigeons. On the other hand, well-developed naturally-occurring lesions contained increased concentrations of collagen but showed no increase proline hydroxylase activity. This is not to say though, that active collagen synthesis and presukably increased proline hydroxylase activity did not take place at some point in the development of these naturally-occurring lesions.