Thiouracil-induced myocardial fibrosis.

Rabbits were fed with thiouracil for 8 months. Subsequently their hearts were examined electron microscopically as well as biochemically for collagen and hexosamine content. Chronic treatment with thiouracil induced an increase in interstitial connective tissue collagen and hexosamine without visible necrosis. As seen by electron microscopy, the increase in collagen content might have been caused by stimulation of the fibrocytes. Furthermore, the heart muscle cells showed deep indentations and bulges of the cell membrane and an enlargement of the T-system.