The effect of renal hypertension on the regional deposition of cholesterol and phospholipid in the aorta of normally- and cholesterol-fed rabbits.

The effect of renal hypertension on dry defatted tissue mass and lipid accumulation in different segments of the aortic intima was studied in both normally-fed and cholesterol-fed rabbits. In normally-fed rabbits hypertension caused an increase in intimal dry weight in the aorta. The increase was greatest in the lower thoracic intimal segment but was not significant in the aortic arch. The increase in tissue mass was not influenced by the addition of cholesterol to the diet and no regression of the increased tissue mass occurred when a 4-week period of hypertension was followed by a 4-week period of normotension. Hypertension did not increase the intimal cholesterol or phospholipid concentrations in normally-fed rabbits, suggesting that an observed increase in lipid content represented the cellular component of the intimal hypertrophy. Hypertension in cholesterol-fed animals caused preferential lipid accumulation in the lower thoracic segment, an effect that was independent of the total intimal cholesterol level. Intimal cholesterol, cholesterol ester and phospholipid were all increased. When a 4-week period of normotension and cholesterol feeding was preceded by a 4-week period of hypertension with normal feeding the amount of cholesterol deposited did not exceed that of the normotensive control, suggesting either that hypertension increased intimal permeability to lipid only in the presence of hypercholesterolaemia, or that healing of damaged intima had occurred before hypercholesterolaemia was fully established.