Effects Of Glycine On Isolated Cardiac Function, Intracellular Free Calcium Concentration And The Release Of TNF-α In Cardiomyocytes During Hypoxia/reoxygenation

Objectives: To observe the effects of glycine on hypoxia-reoxygenation (H/R)-induced myocardial dysfunction, the intracellular free calcium concentration, tumor necrosis factor-a production and the survival rate of cardiomyocytes exposed to H/R, and to further clarify the protection of glycine (GLY) against myocardial I/R injury and its mechanism.Methods: In the first experiment, twenty-nine Spraugue Dawley (SD) rats were randomly divided into four groups: Control (n=7), H/R group (n=8), 0.05% GLY plus H/R group (n=8) and 0.05% GLY group (n=6). A cardiac H/R model was established using a Langendorff isolated heart preparation, and the left ventricular systolic pressure (LVSP), the left ventricular developed pressure (LVDP), the maximum rate of left ventricular pressure rise (dp/dtmax) and fall (dp/dtmin) were observed. In the second part, the primary cultured cardiomyocytes from neonatal rat hearts were divided into seven groups: Control, H/R group, glycine (0.5 mmol/L) plus hypoxia/reoxygenation group, glycine (1.0 mmol/L) plus hypoxia/reoxygenation group, glycine (2.0 mmol/L) plus hypoxia/reoxygenation group, glycine (4.0 mmol/L) plus hypoxia/reoxygenation group, 4.0 mmol/L glycine group. The intracellular free calcium concentration, tumor necrosis factor-a level in supernatant and the survival rate of cardiomyocytes were examined.Results: The results of the cardiac function showed that the LVSP, LVDP, dp/dfmax, dp/dtmin in H/R group decreased after H/R and was lower than those in the other groups at the end of the experiment (P<0.01, P<0.05). After H/R, LVSP, LVDP, dp/dtmax, dp/dtmin in GLY plus H/R group was lower than those in pre-hypoxia, but higher than those in H/R group. The intracellular free calcium concentration of cardiomyocytes in H/R group was higher compared to control (P<0.01). Glycine (0.5-2.0 mmol/L) inhibited the intracellular free calcium concentration elevation induced by H/R in a dose-dependent manner with the optimal inhibitory effect at 2.0 mmol/L. The survival rate of cardiomyocytes increased and the release of tumor necrosis factor-a from cardiomyocytes reduced in glycine (2.0 mmol/L) plus H/R group compared to H/R group (P<0.01, P<0.05).Conclusions: (1) Glycine ameliorates the hypoxia-reoxygenation injury of theisolated rat hearts and can recover the systolic and the diastolic function. (2) Glycine can decrease intracellular free calium concentration and inhibit calcium overload in cardiomyocytes exposed to H/R. (3) Glycine decreases the production of tumor necrosis factor-a and increase the survival rate of H/R-treated cardiomyocytes. (4) These data indicate that protective effects of glycine from H/R-induced myocardial dysfunction could be related to the properties of glycine to inhibit tumor necrosis factor-a release and calcium overload in cardiomyocytes.