Circadian variation of portal, arterial and venous blood levels of melatonin in pigs and its relationship to food intake and sleep
Circadian variation of portal, arterial and venous blood levels of melatonin in pigs and its relationship to food intake and sleep
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DOI：
10.1034/j.1600-079x.2000.280102.x
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发表时间：
2000-01-01
影响因子：
10.3
通讯作者：
Hacker, RR
中科院分区：
文献类型：
--
作者：
Bubenik, GA;Pang, SF;Hacker, RR
研究人员测定了10只幼猪肝门静脉、颅腔静脉和下主动脉中褪黑素的昼夜水平。在麻醉状态下，通过临时插管进入血管，每小时采血一次，共24小时。褪黑素在斑期中期未见峰值，但肝门脉浓度在6时达到峰值。褪黑素的总体水平在肝门静脉中最高（范围35-65 pg/mL），其次是动脉（范围30-55 pg/mL）和腔静脉（范围25-35 pg/mL）。褪黑素的水平在个体猪之间表现出很大的差异，但通常三种来源的平均水平都遵循彼此的时间进程。然而，有时，褪黑素水平在肝门静脉独立于腔静脉的水平变化。大的门脉峰通常在进食期之前出现，并与随后的睡眠期有关。这些数据表明：1)猪外周血中褪黑素的昼夜节律不明显；2)第一次肝脏通道中褪黑素的代谢相对较少；3)食物摄入可能使肝门静脉中的褪黑素水平升高；4)源自胃肠道的褪黑素水平升高可能诱发睡眠。
Circadian levels of melatonin were determined in the hepatic portal vein, cranial vena cava, and the lower aorta of ten juvenile pigs. Blood was sampled every hour for a total of 24 hr via temporary cannulas introduced into blood vessels under anesthesia. No peak levels of melatonin were found in the mid-scotophase, but hepatic portal concentrations peaked at 06.00 hr. Overall levels of melatonin were highest in the hepatic portal vein (range 35-65 pg/mL), followed by an artery (range 30-55 pg/mL) and the vena cava (range 25-35 pg/mL). Levels of melatonin exhibit strong variation between individual pigs, but generally the average levels from all three sources follow each other's time course. However, on occasion, melatonin levels in the hepatic portal vein varied independently from the levels in the vena cava. Large portal peaks were usually preceded by a feeding period and were associated with a subsequent period of sleep. The data indicate that: 1) there is no clear circadian rhythm of melatonin in the peripheral blood of pigs, 2) relatively little melatonin is metabolized during the first liver passage, 3) food intake may elevate melatonin levels in the hepatic portal vein, and 4) increased levels of melatonin originated in the gastrointestinal tract may induce sleep.