Synergistic myoprotection of L-arginine and adenosine in a canine model of global myocardial ischaemic reperfusion injury.

BACKGROUND: Endogenous nitric oxide and adenosine increase simultaneously to keep the balance of energy demand and supply when the oxygen supply is insufficient, which suggests that nitric oxide and adenosine might exert a synergistic myoprotection during tissue hypoxia. In this study, we tested this hypothesis utilizing a canine model of prolonged global myocardial ischaemic reperfusion injury. METHODS: In this double blind, controlled study, the hearts of 24 anaesthetized mongrel dogs were arrested for 2 hours with aortic cross clamping and blood cardioplegia. The treatment groups were those supplemented with 2 mmol/L L-arginine (ARG), supplemented with 1 mmol/L adenosine (ADO), ARG + ADO supplemented with both, and no supplementation (control) (n = 6 in each group). Haemodynamics, biochemical indices, adenosine triphosphate (ATP) content and myeloperoxidase activities of myocardium were determined to evaluate myocardial injury. Statistical comparison was performed by two way ANOVA. RESULTS: Although the requirements for inotropic supports were higher, the cardiac outputs were lower in control group than in ARG, ADO and the combination groups. Plasma cardiac troponin I levels were higher and the areas of hydropic changes were larger in control group than in ARG and ADO groups. Combination of arginine and adenosine provided further myoprotection with respect to better cardiac performance, lower release of cardiac troponin I, and smaller areas of hydropic changes compared with ARG and ADO groups. ATP content was higher, but myeloperoxidase activities of myocardium were significantly lower in the combination group than in control, ARG and ADO groups (P < 0.05). CONCLUSIONS: Combination of L-arginine and adenosine provides synergistic myoprotection in a canine model of global myocardial ischaemia. Thus, the combination is recommended when the heart is exposed to a prolonged ischaemia during cardiac surgery.

[The influence of leukocyte depletion filter-LD-1 on leukocytes, IL-6, MPO and the pathologic changes of myocardic tissues during cardiopulmonary bypass].

OBJECTIVE: To elucidate the influence of the leukocyte depletion filter (LD-1) on leukocytes, IL-6, myeloperoxidase enzyme (MPO) and the pathological changes of myocardic tissues during cardiopulmonary bypass(CPB). METHODS: Twelve dogs were used in this study. The LD-1, designed and made by ourselves, was fixed on the venous line in the trial group (n=6). It was used during the first 5 min after 2 min of CPB. LD-1 was not installed in the control group (n=6). Circulating leukocytes were counted before CPB, at 10 min, 40 min, 75 min during CPB, at the end of CPB, and 2 h after CPB. Plasma levels of IL-6 and MPO were also determined at the same time. The pathologic changes of left ventricular biopsies were observed before CPB, 5 min after protamine was given, and 2 h after CPB. RESULTS: The CPB 10 min WBC Count fell to 36% of that Before CPB in LD-1 group, which was lower than the WBC count in the control group synchronously (P < 0.01). But after CPB 2 h, both of them were close to the levels Before CPB in the two groups. In LD-1 group, IL-6 increased at CPB 40 min and reached to the top. But after wards it dropped continuously. The changes were of no significance in MPO and in the pathological examination of myocardic tissues (P > 0.05). CONCLUSION: The LD-1 on venous line was capable of decreasing WBC count effectively. As a result, the inflammation factors that leukocytes released were lower, so the program chain of inflammation by CPB was shorter. But LD-1 was not superior in myocardial preservation.