Glycogen Regulation in Isolated Perfused Near Term Monkey Liver
Glycogen Regulation in Isolated Perfused Near Term Monkey Liver
复制标题
离体灌注近期猴肝脏中的糖原调节
作者：
J. W. Sparks;A. Lynch;R. Chez;W. Glinsmann
浸提液：采用原位再循环灌注系统，研究了90%妊娠期猴孕体离体灌注肝脏的糖原代谢。葡萄糖和半乳糖的净摄取和酶，糖原合成酶和磷酸化酶的活性，进行了研究，在不同的灌流液组成。合成酶活性表示为% 1，即活性形式的总合成酶活性的百分比。灌注液葡萄糖浓度高达700 mg/100 ml不会导致净葡萄糖摄取或基线%I合成酶增加（4 ± 1，平均值± SEM）。在存在300 mg/100 ml葡萄糖的情况下，10-7 M的胰岛素使%I增加至8 ± 2，而> 75 mg/100 ml的半乳糖使%I增加至8 ± 1。半乳糖、葡萄糖和胰岛素的组合使%I增加至40 ± 5。对于后一种组合，合成酶活性与高于100 mg/100 ml的灌注液葡萄糖浓度成比例。磷酸化酶活性被半乳糖或胰岛素减弱，并且在接受半乳糖、葡萄糖和胰岛素的组中磷酸化酶活性最低。半乳糖被所有肝脏吸收，但在任何条件下均未观察到净葡萄糖摄取;在半乳糖灌注中观察到净己糖摄取。糖原水平并没有显着变化与不同的灌注液组合物在30分钟perfusion periods.Speculation：我们推测，半乳糖可能是唯一重要的新生儿肝糖原合成，其作用是通过相互的变化介导的酶，糖原合成酶和磷酸化酶的活动。如果肝糖原对于急性新生儿葡萄糖稳态是重要的，那么半乳糖也可能是通过确保进食期间的糖原合成来维持循环葡萄糖浓度所必需的。
Extract: Glycogen metabolism was studied in the isolated perfused liver of the monkey conceptus at 90% of gestation using an in situ recirculating perfusion system. Net uptake of glucose and galactose and the activities of the enzymes, glycogen synthetase and phosphorylase, were studied in response to varied perfusate composition. Synthetase activity was expressed as %1, the percentage of total synthetase activity in the active form. Perfusate glucose concentrations as high as 700 mg/100 ml did not lead to net glucose uptake or to an increase in the baseline %I synthetase (4 ± 1, mean ± SEM). In the presence of 300 mg/100 ml glucose, insulin at 10-7 M increased %I to 8 ± 2, and galactose > 75 mg/100 ml increased %I to 8 ± 1. The combination of galactose, glucose, and insulin increased %I to 40 ± 5. With this latter combination, synthetase activity was proportional to perfusale glucose concentration above 100 mg/100 ml. Phosphorylase activity was diminished by either galactose or insulin, and phosphorylase activity was lowest in the group receiving galactose, glucose, and insulin. Galactose was taken up by all livers, but net glucose uptake was not observed under any condition; net hexose uptake was observed in perfusions with galactose. Glycogen levels did not vary significantly with varied perfusate composition during the 30-min perfusion periods.Speculation: We speculate that galactose may be uniquely important for neonatal liver glycogen synthesis, and that its action is mediated through reciprocal changes in the activities of the enzymes, glycogen synthetase and phosphorylase. If liver glycogen is important for acute neonatal glucose homeostasis, then galactose may also be essential for maintaining circulating glucose concentration by ensuring glycogen synthesis during feeding.