Experimental myocardial infarction with cartilaginous and osseous metaplasia in SHR and WKY rats.

Myocardial infarction was induced by ligation of the coronary artery in fifteen 32-week-old male spontaneously hypertensive rats (SHR) and fifteen 32-week-old male normotensive Wistar-Kyoto rats (WKY). Age-matched male SHR (n = 6) and WKY (n = 7) without the operation were used as non-infarcted control rats. Four weeks after the operation, cartilaginous metaplasia and osseous metaplasia were observed histopathologically in all SHR and 13 of the 15 WKY with myocardial infarction, but not in the control rats. The mean rates of infarction to the heart and the mean areas of metaplasia per rat showing metaplasia were greater in SHR than in WKY. The metaplastic areas were well correlated with the infarct percentage in SHR. It is therefore considered that extensive myocardial infarction is associated with the pathogenesis of cartilaginous and osseous metaplasia.