Changes in collagenase and collagen gene expression after induction of aortocaval fistula in rats.

Progressive ventricular dilatation commonly accompanies the transition to overt failure in chronically overloaded hearts; however, only recently have studies begun to elucidate underlying molecular alterations. In particular, the potential role of altered myocardial expression of the procollagenase gene in this process has not previously been examined. Biventricular hypertrophy and dilatation were produced in rats by creating an abdominal aortocaval fistula. The time courses of changes in expression of collagen I and III genes and of the procollagenase gene (matrix metalloproteinase-1, MMP-1) were assessed by Northern blot hybridization. Expression of all three genes increased promptly; however, collagenase gene expression peaked much earlier (8 h) than did expression of either of the collagen genes (7 days), and all returned to baseline levels by 45 days. These data corroborate earlier reports of increased collagen gene expression in this model, but more importantly, they provide the first evidence of concurrent activation of collagenase gene expression, suggesting that enhancement of collagen degradation may be a prerequisite for structural cardiac dilatation.