Hlutkin S, Zinchuk V
Department of Physiology, Grodno State Medical University, Belarus.
Adv Med Sci. 2008;53(2):234-9. doi: 10.2478/v10039-008-0035-7.
We aimed to study effect of melatonin on the blood oxygen transport during hypothermia and rewarming in rats.
MATERIAL/METHODS: Cold exposure was performed on male rats (body weight 220-270 g, n=48) for 120 minutes under the box water temperature of 19 degrees C; rewarming took the next 120 min, with a mean rate of 0.06 degrees C/min. Melatonin was administered intraperitoneally 30 min before the cold exposure (bolus doses of 0.1, 1 or 10 mg/kg, or 1 mg/kg*day for 4 days). Haemoglobin-oxygen affinity was evaluated by p50 (blood pO2 at its 50% O2 saturation) determined by the "mixing" method at 37 degrees C, pH 7.4 and pCO2 40 mm Hg (p50stand) and at actual pH, pCO2 and temperature (p50act).
After hypothermia and rewarming, the values of p50stand and p50act were 31.5+/-0.28 and 30.2+/-0.61 mm Hg, respectively. The 0.1 mg/kg of melatonin virtually did not change these values, whereas the larger doses increased them. This effect was maximal after the prolonged (4 days) melatonin administration: p50stand rose by 5.4% (p<0.05) and p50act--by 12.9 (p<0.05) compared with rats without the melatonin treatment. Melatonin affected the mechanisms of O2 transport by decreasing the haemoglobin-oxygen affinity (shifting the oxygen dissociation curve of haemoglobin rightwards) and promoting the tissue oxygenation, thereby enhancing the body's resistance to cold.
The melatonin effect mediated by haemoglobin-oxygen affinity change may be used for the correction of metabolic disorders and the improvement of the body's resistance to low environmental temperature.
我们旨在研究褪黑素对大鼠低温及复温过程中血液氧运输的影响。
材料/方法：对雄性大鼠（体重220 - 270克，n = 48）在箱内水温19摄氏度的条件下进行120分钟的冷暴露；接下来的120分钟进行复温，平均复温速率为0.06摄氏度/分钟。在冷暴露前30分钟腹腔注射褪黑素（推注剂量为0.1、1或10毫克/千克，或连续4天每天1毫克/千克）。通过在37摄氏度、pH 7.4和pCO2 40毫米汞柱（p50标准值）以及实际pH、pCO2和温度（p50实际值）下采用“混合”法测定的p50（血氧饱和度为50%时的血液pO2）来评估血红蛋白与氧的亲和力。
低温及复温后，p50标准值和p50实际值分别为31.5±0.28和30.2±0.61毫米汞柱。0.1毫克/千克的褪黑素几乎未改变这些值，而较大剂量则使其升高。在长期（4天）给予褪黑素后，这种作用最为明显：与未接受褪黑素治疗的大鼠相比，p50标准值升高了5.4%（p<0.05），p50实际值升高了12.9%（p<0.05）。褪黑素通过降低血红蛋白与氧的亲和力（使血红蛋白的氧解离曲线向右移动）并促进组织氧合，从而影响氧运输机制，进而增强机体的抗寒能力。
由血红蛋白与氧亲和力变化介导的褪黑素作用可用于纠正代谢紊乱并提高机体对低环境温度的抵抗力。
