Glycogenolytic Activity in the Liver of the Human Foetus

Gennser, G.; Lundquist, Ingmar; Nilsson, Erik

doi:10.1159/000240398

Cited by 18 publications

(7 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In a series of studies from this laboratory [4][5][6][15][16][17][18][19][20][21] we have tried to elucidate the possible physiological significance of a lysosomal glycogenolytic hydrolase, the acid amyloglucosidase (an enzyme which can be characterized as an exo-1,4-oc-glucosidase) (EC 3.2.1.3), with special regard to occurrence and activity in liver and muscle tissue and in the pancreatic islets. During these investigations it was observed that administration to mice of a highly purified acid amyloglucosidase of fungal origin [17] resulted in a reduction of liver glycogen and blood glucose levels, while the basal plasma immuno-…”

mentioning

confidence: 99%

Carbohydrate Content and Regulation following Injection of Different Glycogenolytic Enzymes

Lundquist¹

1975

Enzyme

Self Cite

View full text Add to dashboard Cite

The effect of injection of glycogenolytic enzymes on tissue glycogen, blood glucose and plasma insulin was studied in mice. No effects were observed following phosphorylase, whereas the hydrolytic enzymes, α-amylase and acid amyloglucosidase depressed liver glycogen. In addition acid amyloglucosidase induced a decrease in blood glucose, a slight elevation of plasma insulin and a marked increase in tolbutamide-stimulated insulin release. At the doses given none of the enzymes affected muscle glycogen. Amyloglucosidase pretreatment markedly enhanced insulin release induced by glibenclamide, leucine, isoleucine, lysine and glucose whereas insulin release stimulated by IPNA, ACTH, glucagon and ‘CCK-PZ’ was unaffected. Injection of acid amyloglucosidase has a profound influence on carbohydrate content and regulation in mice. It is suggested that the dependence or independence of amyloglucosidase activity among the insulin secretagogues tested might reflect different or partially different mechanisms in the process of insulin secretion.

show abstract

mentioning

confidence: 99%

Carbohydrate Content and Regulation following Injection of Different Glycogenolytic Enzymes

Lundquist¹

1975

Enzyme

Self Cite

View full text Add to dashboard Cite

show abstract

“…In humans, development of rapid glucose and glycogen mobilizing responses precedes birth (1,13,26), and liver glycogen levels, high at birth, decline rapidly during the first few hours of life (3,28). Idiopathic neonatal hypoglycemia does not appear to be associated with impaired glycogenolytic mechanisms since it usually occurs when liver glycogen stores are depleted (3,28).…”

Section: Speculationmentioning

confidence: 99%

Glucose Regulation by Isolated Near Term Fetal Monkey Liver

et al. 1975

View full text Add to dashboard Cite

ExtractNear term fetal monkey livers were perfused with a closed recirculating system and a defined perfusion medium. Livers from normal fetal animals were able to release glucose rapidly into the perfusate when they were exposed to glucagon, cyclic AMP, or an aglycemic perfusate, but they did not remove glucose rapidly from the perfusate, synthesize glycogen, or activate liver glycogen synthetase in response to hyperglycemia (Figs. 1,2, and 3; Table I ). Insulin decreased glucose mobilization in response to aglycemia, but did not stimulate glucose uptake during hyperglycemia; insulin activated glycogen synthetase (Table 1; Figs. 1 and 3). Livers from fetuses of streptozotocin-treated mothers and livers from 2-week-old neonates released more glucose into the perfusate in response to aglycemia then did livers from normal fetal monkeys (Fig. 4). These observations support the possibility that neonatal monkey liver is capable of rapidly mobilizing glucose during periods of hypoglycemia but is unable to take up glucose and store glycogen rapidly during periods of hyperglycernia. SpeculationIncomplete development of glycogen synthetic mechanisms in early postnatal life may contribute to decreased liver glycogen reserves. These decreased reserves may then be inadequate for maintaining normoglycemia during periods of increased glucose uptake or utilization by peripheral tissue. (9,10,27,29) support the possibility that at birth hormonal regulation of glycogen metabolism is competent, but direct glucose regulation of glycogen synthesis has not developed.In humans, development of rapid glucose and glycogen mobilizing responses precedes birth (1, 13, 26), and liver glycogen levels, high at birth, decline rapidly during the first few hours of life (3,28). Idiopathic neonatal hypoglycemia does not appear to be associated with impaired glycogenolytic mechanisms since it usually occurs when liver glycogen stores are depleted (3, 28). Consequently, we considered that incomplete development of glycogen synthetic mechanisms in early postnatal life might contribute to decreased liver glycogen reserves and that these inadequate reserves are incapable of maintaining normoglycemia.We now provide additional support for this possibility based on studies with isolated perfused rhesus monkey livers from near term fetuses of normal mothers and mothers with streptozotocin-induced glucose intolerance, and from normal monkey neonates. In all three groups, hepatic glucose removal rates were low in the presence of high glucose concentrations in the perfusion solution. Changes in circulating glucose concentration did not modify glycogen synthetase activity, but in all instances liver glucose was released in response to hypoglycemia. Direct effects of exogenous glucagon and insulin on hepatic glucose output and glycogen cycle enzyme activity were demonstrated in the near term fetus group. METHODS ANIMALSOne of the primary functions for liver is to maintain blood glucose levels. This is achieved by changes in gluconeogenic Pregnant Macaca mulatt...

show abstract

“…•Gestational age was determined from the nomogram of Tanimura et al 23 fAll dishes containing dibutyryl cyclic AMP also contained theophylline.…”

Section: Studies In Organ Culturementioning

confidence: 99%

Hormonal Regulation of Glycogen Metabolism in Human Fetal Liver: I. Normal Development and Effects of Dibutyryl Cyclic AMP, Glucagon, and Insulin in Liver Explants

1975

View full text Add to dashboard Cite

Glycogen accumulates in human fetal liver beginning at the eighth week of gestation. A parallel increase in total glycogen synthase activity is found, although the I-form activity remains low and constant throughout the first two thirds of gestation. Total phosphorylase activity increases slightly during this period, with the proportion in the active form amounting to about one half of the total throughout. After an initial rapid decline, the glycogen concentration in explants of human fetal liver remained constant for twenty to forty hours at about 20 per cent of the in vivo level. Incubation with glucagon, cyclic AMP (adenosine 3',5'-monophosphate) or its dibutyryl derivative markedly reduced tissue glycogen concentrations while insulin brought about a small increase. The effect of maximal doses of dibutyryl cyclic AMP and glucagon were the same, and the combination of agents produced no further effect. The response to dibutyryl cyclic AMP was apparent by one hour and maximal by three to six hours, whereas the response to insulin required about six hours to be detected, and it continued for at least eighteen hours. Insulin antagonized the glycogenolytic effect of low doses of glucagon or theophylline but was without significant effect in the presence of high glucagon concentrations. Glucagon stimulated cyclic AMP output from explants, and this effect was further augmented by theophylline. Insultin had no consistent effect on cyclic AMP output in either the presence or the absence of glucagon or theophylline. Incubation with dibutyryl cyclic AMP resulted in a decrease of glycogen synthase I-form activity, while insulin tended to increase this enzyme activity. In neither circumstance was the proportion of active phosphorylase altered. These results suggest that the regulation of glycogen levels in human fetal liver by cyclic AMP, glucagon, and insulin may entail alterations in the activity of glycogen synthase activity without necessitating alterations in phosphorylase activity. Cyclic AMP or glucagon was capable of depleting tissue glycogen stores in tissue from fetuses of six weeks' gestation. Insulin increased tissue glycogen concentrations in tissue from fetuses of seven or more weeks.

show abstract

Glycogenolytic Activity in the Liver of the Human Foetus

Cited by 18 publications

References 1 publication

Carbohydrate Content and Regulation following Injection of Different Glycogenolytic Enzymes

Carbohydrate Content and Regulation following Injection of Different Glycogenolytic Enzymes

Glucose Regulation by Isolated Near Term Fetal Monkey Liver

Hormonal Regulation of Glycogen Metabolism in Human Fetal Liver: I. Normal Development and Effects of Dibutyryl Cyclic AMP, Glucagon, and Insulin in Liver Explants

Contact Info

Product

Resources

About