Effect of thiouracil upon canine arterial elastic tissue

Unlike some other mammalian species, the dog is relatively resistant to the development of elevated levels of serum cholesterol after prolonged cholesterol feeding. This may be overcome by suppressing thyroid activity with thiouracil. Information regarding possible activity of thiouracil itself upon the arterial tissues is almost nonexistent. The present investigation was undertaken to test whether this drug has any such action, especially upon the arterial elastic tissues. Destructive changes were observed in arterial elastic tissues in dogs given thiouracil for three and six months. The changes consisted of accentuation of the elastic fibrillar components, formation and subsequent coalescence of clefts, and fragmentation and ultimate "dissolution" of the elastic elements. The results suggest that thiouracil may exert a damaging effect upon the arterial elastic fibers; thus, it is possible that one of the mechanisms by which thiouracil and cholesterol administration induces experimental atherosclerosis in the dog is by elastic tissue destruction, possibly promoting the subsequent lipid accumulation in the arterial wall.