Kinetics of High-Energy Phosphates in Allopurinol-Pretreated Ischaemic and Post-lschaemic Skeletal Muscle: An in vivo Magnetic Resonance Spectroscopy Study

Abstract

AUopurinol (AP) protects skeletal muscle function against ischaemia-induced injury, but the mechanism is not yet clear. As AP acts as a competitive xanthine oxidaxe inhibitor, both a reduction of oxygen-derived free radicals and an enhancement of purine resynthesis (salvage pathway) might be involved. We investigated the in vivo kinetics of high-energy phosphates in skeletal muscle after AP pretreatment using ³¹P-magnetic resonance spectroscopy during 2 h of ischaemia and 3 h of reperfusion in rat hindlimbs. Three animals (group A) were pre-treated with a total of 160 mg/kg AP i.p., 3 control animals (group B) received the same amount of 0.9% saline solution. ATP decreased to 18.6 ± 1.3% of the pre-ischaemic value in group A and to 17.3 ± 2.8% in group B after 2 h of ischaemia, and rose to only 47.7 ± 1.5 and 50.5 ± 1.8%, respectively, after 3 h of reperfusion. Phosphocreatine fell to 7.2 ± 2.9 and 7.6 ± 2.2% of pre-ischaemic values after 2 h of ischaemia and rose again to 36.5 ± 12.9 and 45.4 ± 20.4% after 3 h of reperfusion. Inorganic phosphate (Pi) increased 5-fold after 2 h of ischaemia, irrespective of the treatment. After 3 h of reperfusion, Pi was still 4 times the pre-ischaemic value. The kinetics of ATP, PCr, and Pi levels were not statistically different between the two groups. These results indicate that the ATP salvage pathway does not play an important role in AP-induced attenuation of ischaemia/reperfusion-induced muscle damage.