Effects of magnesium on exercise performance and plasma glucose and lactate concentrations in rats using a novel blood-sampling technique

摘要

Repeated blood sampling in rodents is often necessary and difficult. Magnesium has been touted as an agent fornenhancing physical activity. An auto-blood-sampling device coupled with a microdialysis analyzer was developed to deter-nmine blood glucose and lactate concentrations in rats subjected to treadmill exercise. The effects of magnesium on exercisenperformance and blood energy metabolism were also evaluated. Sprague–Dawley rats fed a magnesium-adequate diet werenrandomly assigned to 2 experimental groups. Exercise performance was evaluated at 3 treadmill speeds (10, 15, andn20 mu0002min–1) with or without magnesium administration (90 mgu0002kg–1, intraperitoneal) in the first experiment. In the othernexperiment, each rat was fitted with a catheter in the jugular vein for collection of blood samples during the treadmill ex-nercise at a speed of 20 mu0002min–1. Exercise performance was significantly higher at the lower speed of 10 mu0002min–1 in thencontrol group. In addition, exercise performance was significantly enhanced only at 20 mu0002min–1 in the magnesium-sulfate-ntreated group when compared with the control group. Blood samples were collected every 15 min. Glucose concentrationsnincreased significantly and then declined immediately after completion of the exercise task at 20 mu0002min–1 in both groups.nHowever, glucose concentrations increased immediately after administration of magnesium and increased further duringnexercise when compared with those of the control group. Findings from a repeated blood-sampling assay suggest that in-ncreased blood glucose contributes to enhanced exercise performance by rats injected intraperitoneally with magnesium.%Le pre ´le `vement re ´pe ´te ´ d’e ´chantillons sanguins chez les rongeurs est souvent ne ´cessaire et difficile. Le magne ´-nsium pourrait e ˆtre un facteur ergoge `ne. Un dispositif d’e ´chantillonnage autonome combine ´ a ` un analyseur de microdialysenest mis au point afin d’e ´valuer les concentrations sanguines de glucose et de lactate chez des rats soumis a ` un effort phy-nsique sur un tapis roulant. On de ´termine aussi l’effet du magne ´sium sur la performance physique et sur le me ´tabolismene ´nerge ´tique sanguin. On re ´partit de fac ¸on ale ´atoire dans 2 groupes expe ´rimentaux des rats Sprague–Dawley recevant unenjuste portion de magne ´sium. Dans la premie `re expe ´rimentation, on e ´value la performance physique des rats recevant ounnon du magne ´sium (90 mgu0002kg–1, i.p.), et ce, a ` 3 vitesses sur le tapis roulant (10, 15 et 20 mu0002min–1). Dans la deuxie `me ex-npe ´rimentation, on inse `re un cathe ´ter dans la veine jugulaire pour le pre ´le `vement des e ´chantillons de sang au cours desnse ´ances d’exercice physique sur tapis roulant a ` une vitesse de 20 mu0002min–1. Comparativement aux re ´sultats note ´s aux deuxnplus hautes vitesses de course, on enregistre une performance physique significativement supe ´rieure chez le groupe dencontro ˆle courant a ` une vitesse de 10 mu0002min–1. De plus, les rats traite ´s au sulfate de magne ´sium pre ´sentent une performancenphysique significativement supe ´rieure seulement a ` la vitesse de 20 mu0002min–1, comparativement aux valeurs du groupe dencontro ˆle. On pre ´le `ve des e ´chantillons de sang toutes les 15 min. Dans les 2 groupes, la concentration de glucose augmentensignificativement puis diminue imme ´diatement apre `s la fin de la se ´ance d’exercice mene ´ea ` une vitesse de 20 mu0002min–1.nComparativement aux valeurs du groupe de contro ˆle, la concentration de glucose augmente imme ´diatement apre `s l’admi-nnistration de magne ´sium et continue d’augmenter au cours de la se ´ance d’exercice. D’apre `s ces observations base ´es sur unnpre ´le `vement re ´pe ´te ´ d’e ´chantillons de sang, l’augmentation de la concentration sanguine de glucose favorise l’ame ´liorationnde la performance physique de rats ayant rec ¸u du magne ´sium par voie intrape ´ritone ´ale.