Lactate Uptake In Rabbit Brain During Acute Hypoglycemia When The Lactate Level Elevated And The Effect On Hypoglycemic Brain Damage

Object:This study was undertaken to examine directly the uptake of glucose and lactate by the brain, during hypoglycemia. Use the morphologic study to test that when circulating lactate were elevated, whether it could prevent the hypoglycemic brain damage.Methods and material:Female adult rabbits (2.5±0.7kg body weight), the number is 16. Those subjects were random divided into two different groups:lactate group and control group. Both groups were fasted 24 hours. The rabbits were anesthetized by sodium pentobarbital I.V. in a dose of 30mg per kilogram plus 5 mg per kilogram*h. Ventilated via tracheostomy with 21% O2. Polyethylene catheters were positioned in the inter jugular venous bulb(for sampling) and femoral artery (for sampling and blood pressure recording).Thermostated heaters were used to keep rectal temperature at37.5±1.0℃. In lactate group, the blood lactate concentration was elevated by infusion a 0.6mmol*1-1 sodium lactate. The lactate was infused via a sterile catheter at a rate of 50μmmol*kg-1*min-1 for 20 minutes, and was reduced thereafter to a rate of 30μmmol*kg-1*min-1 for the remainder of the study. In the control group the1.24% sodium bicarbonate were infused via venous instead of sodium lactate, to mimic the pH change in blood induced by the sodium lactate. When the time=2h, both group were induced hypoglycemia by I.V. injection of regular insulin at the rate of lu*Kg-1*min-1 for 1.5 hours.The sample of lactate and glucose were drawn from jugular venous bulb and femoral artery simultaneously, the time interval is 1 hour. At the time points of time=-lh, time=-30min, time=0h, time=1h, time=2h, time=3h, time=4h, time=5h, time=6h respectively. Those sample were measured the concentration of glucose and lactate. Then the amount of glucose and lactate which uptake by brain were measured by the A-IJV difference (femoral artery lactate-inner jugular venous lactate, femoral artery glucose -inner jugular venous lactate).Kill those rabbits by infuse sodium pentobarbital I.V. in a dose of 60mg per kilogram. Stain the brain slice by HE, and then examine the slice of brain cortex in microscopes. When find the cell increased the affinity for acid dye and find the number of apoptosis body was increased in brain cortex slice. It is the sign of hypoglycemic brain damage.Result1 The ANOVA was used to compare the mean arterial pressure between the lactate group and control group. There was no difference in mean arterial pressure between the lactate group, control group and the normal subject, the p=0.396>0.05. Mean there is no hypoperfusion during this study.2 The one-way ANOVA for repeated measurements was applied for comparison of the uptake of lactate between the lactate group and control group. There was significant difference in lactate uptake by brain between the lactate group and control group, the p=0.02<0.05. Mean the lactate group uptake more lactate than the control group after the lactate elevated. And the difference relate to the lactate concentration but did not relate to the period of time.3 There was no difference in lactate uptake between lactate concentration elevated and the normal concentration in control group, the p=0.06>0.05. Mean the lactate uptake did not change in control group during the study.4 The one-way ANOVA for repeated measurements was applied for comparison of the uptake of glucose between the lactate and control group. There was no significant difference in glucose uptake between the lactate group and control group, the p=0.639>0.05. Mean there is no difference between the lactate group and control group in glucose uptake during this study.5 Useχ2analysis was applied to test the case of hypoglycemic brain damage between lactate group and control group. The p=0.596>0.05. Mean there is no difference between the two groups in the case of hypoglycemia brain damage.Conclusion1 When the lactate concentration were elevated 3-5 fold, the lactate uptake by brain in adult rabbit was significant difference between lactate group and control group. The former uptake more lactate during study. This difference related to the lactate concentration and did not relate to the period of time2 The glucose uptake between lactate group and control group were no difference in this study. The concentration of glucose and lactate could not influence the glucose uptake by brain in this study.3 The concentration of lactate although elevated in this study in lactate group, and the lactate uptake was elevate correspond to those change. The alternation could not prevent the acute hypoglycemic brain damage in this study.