Suppression of calcific fibrous-fatty plaque formation in rabbits by agents not affecting elevated serum cholesterol levels. The effect of thiophene compounds.

We tested the suppressive effect of antihypercalcemic-hyperphosphatemic agents on atherogenesis. We studied five groups of rabbits for 8 weeks, one control group and four groups on a fibrogenic atherogenic diet. One group received the atherogenic diet alone, and the remaining three atherogenic groups were treated simultaneously with 2-thiophenecarboxylic acid (ThCA), 5-methyl-2-thiophenecarboxylic acid (5-CH3-ThCA), and 5-bromo-2-thiophenecarboxaldehyde (5-Br-ThCA). Rabbits receiving the atherogenic diet alone developed: (1) elevations of serum cholesterol, calcium, and phosphorus; (2) massive fibrous-fatty aortic plaques with excessive accumulation of aortic collagen, elastin, and lipids; (3) marked deposition of calcium and phosphorus in both aortic tissue and elastin; and (4) severe lipid infiltration of the liver. Treatment with all three drugs normalized the elevated serum calcium but not the cholesterol levels, and effectively inhibited all aspects of the atherosclerotic process as determined morphologically and biochemically. The order of effectiveness was: 5-CH3-ThCa greater than 5-Br-ThCA greater than ThCA. No bone resorption occurred in the treated groups. The normalizing effects of the thiophene compounds on serum phosphorus levels were not significant at the dosages used.