Bashan N, Gross Y, Moses S, Gutman A
Biochim Biophys Acta. 1979 Oct 4;587(2):145-54. doi: 10.1016/0304-4165(79)90349-0.
The correlation between blood glucose levels, the concentration of glycogen, the activities of glycogen synthase and phosphorylase and their respective kinases and phosphatases was examined in liver of rat fetuses between day 18 of gestation and one day after birth. Between day 18 and 21 there is a rapid increase in the concentration of glycogen and in the activity of synthase a and a much slower increase in the activity of phosphorylase a. The activity of the respective kinases increased rapidly during this period and reached maximum on day 21. The activity of synthase phosphatase and phosphorylase phosphatase increased after day 18, to reach a maximum on day 19 and 20, respectively, but decreased again towards day 21. The possibility that the changes in glycogen concentration and enzyme activities were related to an effect of glucose or AMP on the respective phosphatases was considered. It was found that the Km of phosphorylase phosphatase for glucose in the prenatal period was 5--7 mM, as in the adult. Since the level of blood glucose during this period was constant (2.8 mM), an effect of glucose on phosphatase activity seems unlikely. AMP concentration increased between day 18 and 21 from 6--15 nmol/g. In view of the low level of phosphorylase a activity during this period, the increase in AMP concentration is not considered to be important in the regulation of glycogen breakdown at this time. Immediately after birth blood glucose levels dropped to 5 mg/dl. This was accompanied by a rapid decrease in glycogen concentration and in the activity of glycogen synthase and a rise in phosphorylase activity. Blood glucose levels returned to the initial level within 1 h after birth, whereas the changes in glycogen concentration and enzyme activities continued for at least 3 h after birth. On day 22 all parameters examined had reached the level found in adult rat liver. It is suggested that the rapid changes observed immediately after birth are due to an effect of gypoglycemia mediated by hormones and cannot be ascribed to direct effects of metabolites on the enzyme systems involved.
对妊娠第18天至出生后1天的大鼠胎儿肝脏中血糖水平、糖原浓度、糖原合酶和磷酸化酶的活性及其各自的激酶和磷酸酶之间的相关性进行了研究。在第18天至21天之间，糖原浓度和合成酶a的活性迅速增加，而磷酸化酶a的活性增加则慢得多。在此期间，各自激酶的活性迅速增加，并在第21天达到最大值。合成酶磷酸酶和磷酸化酶磷酸酶的活性在第18天后增加，分别在第19天和第20天达到最大值，但在接近第21天时又下降。考虑了糖原浓度和酶活性的变化与葡萄糖或AMP对各自磷酸酶的作用有关的可能性。结果发现，产前阶段磷酸化酶磷酸酶对葡萄糖的Km值与成年大鼠一样，为5-7 mM。由于在此期间血糖水平恒定（2.8 mM），因此葡萄糖对磷酸酶活性的影响似乎不太可能。第18天至21天之间，AMP浓度从6-15 nmol/g增加。鉴于在此期间磷酸化酶a的活性水平较低，此时AMP浓度的增加在糖原分解的调节中并不被认为是重要的。出生后立即，血糖水平降至5 mg/dl。这伴随着糖原浓度和糖原合酶活性的迅速下降以及磷酸化酶活性的升高。出生后1小时内血糖水平恢复到初始水平，而糖原浓度和酶活性的变化在出生后至少持续3小时。在第22天，所有检测参数均达到成年大鼠肝脏中的水平。提示出生后立即观察到的快速变化是由激素介导的低血糖效应引起的，而不能归因于代谢物对所涉及酶系统的直接作用。
