OBJECTIVETo investigate the protective effect of glycine (Gly) on hypoxic rat myocardial cells and its mechanism.

METHODSSdfetal rat myocardial cells were isolated and cultured in vitro. The released amounts of creatine kinase (CK) and lactate dehydrogenase (LDH) from the myocardial cells in the culture supernatant at 6 hour after hypoxia and after glycine treatment were determined with ultraviolet spectrophotometer. The expression of the alpha1 subunits of glycine receptor (GlyRalpha1) in the myocardial cells was detected by immunofluorescent histochemistry. The changes in the intracellular calcium content and the membrane potential of the myocardial cells were determined by laser confocal microscopy.

RESULTSThe release of CK and LDH in the culture supernatant increased significantly at 6 h after hypoxia [(393.8 +/- 5.3), (1564 +/- 41) U/L] compared with those before hypoxia, while their levels were obviously decreased after glycine treatment [(56.3 +/- 2.7), (716 +/- 18) U/L, (P <0.01)] compared with those before glycine treatment. There was positive expression of GlyRalpha1 in myocardial cells before and after hypoxia. The average fluorescent intensity of intracellular calcium at 6 hours after hypoxia (139 +/- 29) was significantly higher than that before hypoxia (27 +/- 8, P < 0.01), while it was obviously lower (51 +/- 11) after glycine treatment compared with that at 6 hours after hypoxia,but it was evidently higher than that before hypoxia (P <0.01). The membrane potential 6 hours after hypoxia (62 +/- 9) was obviously lower than that before hypoxia (177 +/- 20, P < 0.01), but it was obviously higher after glycine treatment (123 +/- 16) than that at 6 hours after hypoxia (P < 0.01).

CONCLUSIONGlycine might be beneficial in the protection of myocardial cells against hypoxia. The underlying mechanism may involve attenuation of membrane potential depolarization after hypoxia by conjugation of glycine with its receptor, depleting in turn voltage-dependent calcium channel on the cellular membrane, preventing calcium overload due to influx of calcium ions after hypoxia.