Cardioprotective effects of l-glutamine in an ischemic rat heart model

l-glutamine has been shown to have cardioprotective effects in models of ischemia-reperfusion injury. Its potential cardioprotective effects when given before and during early reperfusion, however, have not been studied.

This study hypothesized that l-glutamine administered before and after myocardial ischemia provides better cardioprotection than when administered after ischemia only. Eighteen male rat hearts were exposed to 15 min of ischemia using the Langendorff system and randomly assigned to three groups of six each. Group one received Krebs-Henseleit (KH) buffer over 20 min before ischemia and during 20 min of reperfusion (Control), group two received KH buffer containing 2.5 mmol･L^-1 glutamine during reperfusion (Post-Gln) and group three was given KH buffer containing glutamine before and after the ischemic insult (Pre + Post-Gln). Indicators of hemodynamics such as maximum left ventricular derivative of pressure development (LV dP/dt max) were recorded at 5, 10, 15 and 20 min post-reperfusion. Myocardial levels of O-linked β-N-acetylglucosamine (O-GlcNAc) and heat shock protein 70 (HSP70) were measured by Western blotting technique after 20 min of reperfusion.

The LV dp/dt max in the Pre + Post-Gln group was significantly elevated as compared to the Post-Gln group after 10 min of reperfusion and was significantly higher than in the control group at all-time points. Myocardial expression of O-GlcNAc was increased in the Pre + Post-Gln group (P < 0.01 vs. control) without showing any differences in HSP70.

In this model of stunned myocardium, pre- and post-ischemic administration of l-glutamine improved cardiac function indicating cardioprotective effects, possibly mediated by O-GlcNAc.