OBJECTIVETo study possible correlation between matrix metalloproteinases (MMPs) activities and myocardial injury after asphyxia in neonatal Wistar rats.

METHODSixty neonatal Wistar rats (7 to 10 days old) were randomly divided into four groups: control group (group D); asphyxia groups A, B and C (1 day, 7 days, 14 days after asphyxia), every group had 15 rats. In the asphyxia groups, animal model was produced by normobaric asphyxia. Groups A, B and C were sacrificed on days 1, 7 and 14 days after asphyxia, and group D rats were sacrificed on the 7 th day. Then the heart blood was taken to tested the serum cTnI. The myocardial MMPs-3 and 9 activity was measured by using immunohistochemical assay. Histological sections of the hearts were stained with hematoxylin-eosin and myocardial histopathological scores were determined under an optical microscope. The amount of myocardial collagen was measured by means of chloramines T.

RESULTScTnI was significantly higher in group A (0.3680 +/- 0.40 ng/ml) than group D (0.0783 +/- 0.06 ng/ml) (P < 0.05), and was lower in group B (0.1889 +/- 0.15 ng/ml) but still significantly different from that of group D (P < 0.05), and declined to the normal level in group C (0.1338 +/- 0.07 ng/ml), but the difference between groups C and D was not significant (P > 0.05). Myocardial tissue MMPs-3 activity was transiently high in group A (0.1847 +/- 0.04), higher in group B (0.2780 +/- 0.05) as compared to group D (0.1213 +/- 0.03) (P < 0.05 for all). The activity of MMPs-3 increased earlier than that of MMPs-9. The amount of myocardial collagen of group B (38.94 +/- 0.67) and C (40.69 +/- 0.75) was significantly greater than that of group D (P < 0.05). Myoardial tissue MMPs-3 and MMPs-9 positively correlated with myocardial histopathological scores (r = 0.669, 0.667, P < 0.05) and myocardial collagen (r = 0.482, 0.679, P < 0.05).

CONCLUSIONSIn rats with asphyxia, there was an excess activation of myocardial MMPs-3 and MMPs-9 activities and secondary to which, the quantity of myocardial collagen increased. The injuries of myocardium may be closely associated with myocardial tissue MMPs. MMPs may be used to evaluate the severity of myocardial interstitial damage.