L-glutamate and glutamine improve haemodynamic function and restore myocardial glycogen content during postischaemic reperfusion: A radioactive tracer study in the rat isolated heart

L-Glutamate and glutamine have been suggested to have cardioprotective effects. However, the issue is controversial and the metabolic mechanisms underlying a beneficial effect are not well understood. In the present study we investigated the effects of L-glutamate and glutamine on haemodynamic recovery, the rate of de novo glycogen synthesis and myocardial glucose uptake during postischaemic reperfusion. . Hearts from male Wistar rats (250-300 g) were divided into three groups as follows: (i) control (n = 12); (ii) L-glutamate (n = 12); and (iii) glutamine (n = 12). Hearts were mounted in a Langendorff preparation and perfused with oxygenated Krebs'-Henseleit solution at 80 mmHg and 37C. Global ischaemia for 20 min was followed by 15 min reperfusion, during which L-glutamate (50 mmol/L) or glutamine (20 mmol/L) were administered. Left ventricular developed pressure (LVDP), de novo synthesis of glycogen using [C-14]-glucose and myocardial glucose uptake using D-[2-H-3]-glucose were measured. L-Glutamate and glutamine increased postischaemic LVDP (P < 0.01 vs control hearts for both). L-Glutamate and glutamine increased de novo glycogen synthesis by 78% (P < 0.001) and 55% (P < 0.01), respectively. At the end of reperfusion, total myocardial glycogen content was increased by both L-glutamate and glutamine (5.7 +/- 0.3 and 6.2 +/- 0.7 mmol/g wet weight, respectively; P < 0.05 and 0.01, respectively) compared with that in control hearts (3.6 +/- 0.4 mmol/g wet weight). Neither L-glutamate nor glutamine affected myocardial glucose uptake during reperfusion. . Improved postischaemic haemodynamic recovery after L-glutamate and glutamine supplementation during reperfusion is associated with increased de novo glycogen synthesis, suggesting a favourable modulation of intracellular myocardial carbohydrate metabolism.