OBJECTIVEThe underlying mechanisms for cardiac dysfunction in sepsis include the inhibitory effect of endotoxin and inflammatory factors on myocardium and the decrease in cardiac myocardial cells in number. However, whether there is ventricular remodeling resulted from the abnormalities of extracellular collagen metabolism and whether glutamine (Gln) can protect myocardium from LPS-induced damage as in reperfusion are unknown. The aim of the present study was to examine the effects of Gln on the expressions of matrix metalloproteinase-3 (MMP-3), tissue inhibitor of metalloproteinase-3 (TIMP-3) and their mRNA in myocardium of rats with sepsis.

METHODSClassical rat model of sepsis was established by intraperitoneal injection of lipopolysaccharide (LPS) (4 mg/kg, from Escherichia coli O(55): B(5), Sigma). from 121 Wistar rats aged 18 days were divided into three groups randomly, 0 h control group (normal saline: 1 ml/kg, n = 11), LPS group (LPS: 4 mg/kg, n = 55) and Gln group (LPS: 4 mg/kg and immediately 13.64% glutamine 1 ml/kg, Fresenus, n = 55). Furthermore, LPS and Gln groups were examined at 2 h, 4 h, 6 h, 24 h and 72 h time points (n = 11). On each time point, rats of LPS and Gln groups as well as control group were anesthetized with 1% chloral hydrate injected intraperitoneally at a dosage of 1 ml/kg. Then, rats were sacrificed, and the hearts were isolated. Eight of them were frozen at minus 80 degrees C to measure the expression of TIMP-3 mRNA by using RT-PCR. The expressions of MMP-3 and TIMP-3 were observed with immunohistochemistry and the expression of MMP-3 mRNA was observed by using in situ hybridization.

RESULTS(1) Compared to 0 h, the mRNA expressions of MMP-3 and TIMP-3 in LPS group significantly increased (P < 0.01) with the peak at 6 - 24 h. While, in Gln group, they were significantly higher than those in controls but significantly lower than those in LPS group with the peak at 24 h (P < 0.01). Even at 72 h, they were still higher than those at 0 h (P < 0.05 and P < 0.01). (2) Compared to 0 h, the expressions of MMP-3 and TIMP-3 in LPS group were significantly lower at any other time point with the lowest at 6 h (P < 0.01). In Gln group, these expressions were also significantly lower than those in controls, but significantly higher than those in LPS group with the lowest being postponed to 24 h (P < 0.01). (3) The ultra structure changed obviously. Z line was unclear and the ridge of mitochondrion disappeared. While, in Gln group, the myocardial injury was slight compared to that in LPS group.

CONCLUSIONSMMP-3 mRNA expression was increased and TIMP-3 mRNA expression was depressed in LPS-induced sepsis. Myocardial extracellular matrix was damaged in sepsis. Glutamine might decrease the effects of LPS on MMP-3 and TIMP-3 expressions and postpone the time of myocardial matrix injury.