Sustained hepatic and renal glucose-6-phosphatase expression corrects glycogen storage disease type Ia in mice

Deficiency of glucose-6-phosphatase (G6Pase), a key enzyme in glucose homeostasis, causes glycogen storage disease type Ia (GSD-Ia), an autosomal recessive disorder characterized by growth retardation, hypoglycemia, hepatomegaly, nephromegaly, hyperlipidemia, hyperuricemia, and lactic acidemia. G6Pase is an endoplasmic reticulum-associated transmembrane protein expressed primarily in the liver and the kidney. Therefore, enzyme replacement therapy is not feasible using current strategies, but somatic gene therapy, targeting G6Pase to the liver and the kidney, is an attractive possibility. Previously, we reported the development of a mouse model of G6Pase deficiency that closely mimics human GSD-Ia. Using neonatal GSD-Ia mice, we now demonstrate that a combined adeno virus and adeno-associated virus vector-mediated gene transfer leads to sustained G6Pase expression in both the liver and the kidney and corrects the murine GSD-Ia disease for at least 12 months. Our results suggest that human GSD-Ia would be treatable by gene therapy.     

Heterogeneous mutations in the glucose-6-phosphatase gene in Japanese patients with glycogen storage disease type Ia

Glycogen storage disease type Ia (GSD-Ia) is an autosomal recessive disorder of glycogen metabolism caused by glucose-6-phosphatase (G6Pase) deficiency. It is characterized by short stature, hepatomegaly, hypoglycemia, hyperuricemia, and lactic acidemia. Various mutations have been reported in the G6Pase gene (G6PC). However, in Japanese patients, a g727t substitution was found to be the major cause of GSD-Ia, accounting for 20 of 22 mutant alleles [Kajihara et al., 1995], and no other mutations have been found in this population. We analyzed four Japanese GSD-Ia patients and identified three other mutations in addition to the g727t. They included two missense mutations (R83H and P257L) and one nonsense mutation (R170X). Each of the three mutations exhibited markedly decreased G6Pase activity when expressed in COS7 cells. A patient homozygous for R170X showed multiple episodes of profound hypoglycemia associated with convulsions, while P257L was associated with a mild clinical phenotype. The presence of R170X in three unrelated families may implicate that it is another important mutation in the etiology of GSD-Ia in Japanese patients. Thus, the detection of non-g727t mutations is also important in establishing the DNA-based diagnosis of GSD-Ia in this population.     

Cytochemical identification of cerebral glycogen and glucose-6-phosphatase activity under normal and experimental conditions. II. Choroid plexus and ependymal epithelia, endothelia and pericytes

Summary Intracellular glycogen and glucose-6-phosphatase (G6Pase) activity were identified cytochemically within epithelia of the choroid plexus and ependyma of the cerebral ventricles including the median eminence and area postrema, the cerebral endothelium and pericytes from control, salt-stressed and fasted adult mice. Identification of glycogen was obtained by employing osmium tetroxide-potassium ferrocyanide and the periodic acid-thiocarbohydrazide-silver protein technique as ultrastructural contrast stains. A lead-capture method was used to localize G6Pase activity with glucose-6-phosphate or mannose-6-phosphate as substrate. Cerebral G6Pase functions predominantly as a phosphohydrolase to convert glucose-6-phosphate to glucose. Some glucose-6-phosphatein vivo may be derived from the breakdown of glycogen stores. Within the sampled cell types, presumptive glycogen appeared as electron-dense, isodiametric particles scattered throughout the cytoplasm. Reaction product for G6Pase activity was localized consistently within the lumen of the nuclear envelope and endoplasmic reticulum and frequently within an outer saccule of the Golgi complex under normal conditions. Choroid plexus epithelia from stressed mice exhibited a qualitative increase in cytoplasmic glycogen and a decrease in G6Pase activity; the other cell types did not express demonstrable alterations in glycogen concentration and G6Pase activity. The results indicate that glycogen and G6Pase activity are prevalent within non-neural cells of the adult mammalian CNS. Glucose utilization in the choroid plexus epithelium may be altered by stressful conditions that influence the functional activity of this cell.     

Glycogen storage disease type Ia: molecular diagnosis of 51 Japanese patients and characterization of splicing mutations by analysis of ectopically transcribed mRNA from lymphoblastoid cells

Glycogen storage disease type Ia (GSD-Ia) is an autosomal recessive disorder of glycogen metabolism caused by a deficiency of glucose-6-phosphatase (G6Pase) that is expressed in the liver, kidney, and intestinal mucosa. Clinical manifestations include short stature, hepatomegaly, hypoglycemia, hyperuricemia, and lactic acidemia. To elucidate a spectrum of the G6Pase gene mutations and their frequencies, we analyzed mutations in 51 unrelated Japanese patients with GSD-Ia. The most prevalent mutation was g727t, accounting for 88 of 102 mutant alleles examined, followed by R170X mutation, which accounted for 6 mutant alleles, and R83H mutation which was observed in 3 mutant alleles. In addition, 3 different, novel mutations, IVS1-1g相似文献   

Gene therapy for type I glycogen storage diseases

The type I glycogen storage diseases (GSD-I) are a group of related diseases caused by a deficiency in the glucose-6-phosphatase-alpha (G6Pase-alpha) system, a key enzyme complex that is essential for the maintenance of blood glucose homeostasis between meals. The complex consists of a glucose-6-phosphate transporter (G6PT) that translocates glucose-6-phosphate from the cytoplasm into the lumen of the endoplasmic reticulum, and a G6Pase-alpha catalytic unit that hydrolyses the glucose-6-phosphate into glucose and phosphate. A deficiency in G6Pase-alpha causes GSD type Ia (GSD-Ia) and a deficiency in G6PT causes GSD type Ib (GSD-Ib). Both GSD-Ia and GSD-Ib patients manifest a disturbed glucose homeostasis, while GSD-Ib patients also suffer symptoms of neutropenia and myeloid dysfunctions. G6Pase-alpha and G6PT are both hydrophobic endoplasmic reticulum-associated transmembrane proteins that can not expressed in soluble active forms. Therefore protein replacement therapy of GSD-I is not an option. Animal models of GSD-Ia and GSD-Ib that mimic the human disorders are available. Both adenovirus- and adeno-associated virus (AAV)-mediated gene therapies have been evaluated for GSD-Ia in these model systems. While adenoviral therapy produces only short term corrections and only impacts liver expression of the gene, AAV-mediated therapy delivers the transgene to both the liver and kidney, achieving longer term correction of the GSD-Ia disorder, although there are substantial differences in efficacy depending on the AAV serotype used. Gene therapy for GSD-Ib in the animal model is still in its infancy, although an adenoviral construct has improved the metabolic profile and myeloid function. Taken together further refinements in gene therapy may hold long term benefits for the treatment of type I GSD disorders.     

Mutations in the glucose-6-phosphatase-alpha (G6PC) gene that cause type Ia glycogen storage disease

Glucose-6-phosphatase-alpha (G6PC) is a key enzyme in glucose homeostasis that catalyzes the hydrolysis of glucose-6-phosphate to glucose and phosphate in the terminal step of gluconeogenesis and glycogenolysis. Mutations in the G6PC gene, located on chromosome 17q21, result in glycogen storage disease type Ia (GSD-Ia), an autosomal recessive metabolic disorder. GSD-Ia patients manifest a disturbed glucose homeostasis, characterized by fasting hypoglycemia, hepatomegaly, nephromegaly, hyperlipidemia, hyperuricemia, lactic acidemia, and growth retardation. G6PC is a highly hydrophobic glycoprotein, anchored in the membrane of the endoplasmic reticulum with the active center facing into the lumen. To date, 54 missense, 10 nonsense, 17 insertion/deletion, and three splicing mutations in the G6PC gene have been identified in more than 550 patients. Of these, 50 missense, two nonsense, and two insertion/deletion mutations have been functionally characterized for their effects on enzymatic activity and stability. While GSD-Ia is not more prevalent in any ethnic group, mutations unique to Caucasian, Oriental, and Jewish populations have been described. Despite this, GSD-Ia patients exhibit phenotypic heterogeneity and a stringent genotype-phenotype relationship does not exist.     

Effects of actinomycin D on dexamethasone induced hepatic glycogen accumulation: Morphological and biochemical observations

Effects of inhibition of protein synthesis by actinomycin D (ACT) on the acute stimulation of hepatic gluconeogenesis and glucose-6-phosphatase (G6Pase) by the glucocorticoid, dexamethasone (DEX), in adrenalectomized (ADX) rats, were investigated using both morphological and biochemical means. Examination of ultra-thin sections of liver in the electron microscope revealed that ACT, administered alone or with DEX, resulted in a failure of hepatic glycogen accumulation to occur. Smooth endoplasmic reticulum (SER) appeared similar to that of the ADX-untreated animals, with occasional suggestions of increased amounts of membrane in ACT-treated animals. G6Pase activity in homogenates was increased, as was activation of the enzyme under all experimental conditions, when compared with ADX-untreated controls. The DEX-induced increase in G6Pase activity in SER failed to occur to any appreciable extent in ACT-treated animals. Plasma glucose levels increased slightly when ACT and DEX were present simultaneously. It is suggested that ACT countered the inductive effects of DEX on hepatic glycogen synthesis, but only partially suppressed acute stimulation of gluconeogenesis. A possible superinduction of G6Pase enzyme synthesis through increased efficiency of translation of extant mRNA is discussed. It is proposed that ACT inhibited the formation of appropriate SER membranes and/or other components necessary for glycogen accumulation.     

Molecular genetics of type 1 glycogen storage disease

Glycogen storage disease type 1 (GSD 1) comprises a group of autosomal recessive inherited metabolic disorders caused by deficiency of the microsomal multicomponent glucose-6-phosphatase system. Of the two known transmembrane proteins of the system, malfunction of the catalytic subunit (G6Pase) characterizes GSD 1a. GSD 1 non-a is characterized by defective microsomal glucose-6-phosphate or pyrophosphate/phosphate transport due to mutations in G6PT (glucose-6-phosphate translocase gene) encoding a microsomal transporter protein. Mutations in G6Pase and G6PT account for approximately 80 and approximately 20% of GSD 1 cases, respectively. G6Pase and G6PT work in concert to maintain glucose homeostasis in gluconeogenic organs. Whereas G6Pase is exclusively expressed in gluconeogenic cells, G6PT is ubiquitously expressed and its deficiency generally causes a more severe phenotype. Rapid confirmation of clinically suspected diagnosis of GSD 1, reliable carrier testing, and prenatal diagnosis are facilitated by mutation analyses of the chromosome 11-bound G6PT gene as well as the chromosome 17-bound G6Pase gene.     

Significance of the increase in glucose 6-phosphatase activity in skeletal muscle cells of the mouse by starvation

The effects of starvation on glucose 6-phosphatase (G6Pase; EC 3.1.3.9., D-glucose 6-phosphate phosphohydrolase) and glycogen phosphorylase (EC 2.4.1.1.) activities, and on glycogen content, were studied in skeletal muscles (m. rectus femoris) of mice. In the muscle cells from fed animals, the cytochemical reaction product for G6Pase activity was observed in moderate amounts in the terminal cisternae of sarcoplasmic reticulum and in small amounts in the nuclear envelope, and was rare or absent in the intermyofibrillar sarcoplasmic reticulum. After 4 days of starvation, however, the reaction product became abundant in all of the terminal cisternae, intermyofibrillar sarcoplasmic reticulum, and nuclear envelope. Biochemical G6Pase and glycogen phosphorylase a (active form) activities were higher in the muscles of starved mice than in those of fed animals. The glycogen content decreased markedly in the muscles of starved mice. The results suggest that the role of the increased G6Pase in skeletal muscle cells of starved mice is to release glucose into the blood by hydrolyzing glucose 6-phosphate produced through the increased phosphorylase activity.     

Glycogen storage disease type Ia: four novel mutations (175delGG, R170X, G266V and V338F) identified. Mutations in brief no. 220. Online

Deficient activity of glucose-6-phosphatase (G6Pase) causes glycogen storage disease type Ia (GSD Ia). We analysed the G6Pase gene of 16 GSD Ia patients using single strand conformation polymorphism (SSCP) analysis prior to automated sequencing of exon(s) revealing an aberrant SSCP pattern. In all GSD Ia patients we were able to identify mutations on both alleles of the G6Pase gene, indicating that this method is a reliable procedure to identify mutations. Four novel mutations (175delGG, R170X, G266V and V338F) were identified.     

Glycogen storage disease type Ia in Argentina: two novel glucose-6-phosphatase mutations affecting protein stability

Glycogen storage disease type Ia (GSD-Ia) is caused by deleterious mutations in the glucose-6-phosphatase gene (G6PC). A molecular study of this gene was carried out in 11 Argentinean patients from 8 unrelated families. Four missense (p.Gln54Pro, p.Arg83Cys, p.Thr16Arg, and p.Tyr209Cys) and one deletion (c.79delC) mutations have been identified. Two novel mutations, p.Thr16Arg (c.47C>G) located within the amino-terminal domain and p.Tyr209Cys (c.626A>G) situated in the sixth transmembrane helix, were uncovered in this study. Site-directed mutagenesis and transient expression assays demonstrated that both p.Thr16Arg and p.Tyr209Cys mutations abolished enzymatic activity as well as reduced G6Pase stability.     

Carbohydrate metabolism in human renal clear cell carcinomas.

BACKGROUND: Renal cell carcinomas can be subclassified into clear cell carcinomas, chromophobe cell carcinomas, chromophilic cell carcinomas, and oncocytomas. Previous studies, in which no distinction among the different types of renal cell tumors and their grades of malignancy was performed, showed that these tumors had high glycolytic rates. EXPERIMENTAL DESIGN: The carbohydrate metabolism of control human kidney samples and renal clear cell carcinomas with different degrees of cytologic malignancy (G I, G II, and G III) was studied by determining the glycogen and glucose-6-phosphate levels and the activities of key enzymes involved in glycolysis (hexokinase, glucokinase, pyruvate kinase), gluconeogenesis (glucose-6-phosphatase, fructose-1,6-diphosphatase), and the pentose phosphate pathway (glucose-6-phosphate dehydrogenase) in these tissues and compared with those of a limited number of chromophilic cell carcinomas, chromophobe cell carcinomas, and oncocytomas. RESULTS: The glycogen and glucose-6-phosphate levels were significantly higher in G I, G II, and G III clear cut carcinomas than in control kidneys; glucokinase, hexokinase, and glucose-6-phosphate dehydrogenase activities remained unchanged, pyruvate kinase activity was enhanced, and glucose-6-phosphatase as well as fructose-1,6-diphosphatase activities were strongly reduced when compared with control kidney values. In chromophilic cell carcinomas glycogen content, glucose-6-phosphate dehydrogenase, and pyruvate kinase activities were elevated, while fructose-1,6-diphosphatase activity was reduced. In chromophobe cell carcinomas glycogen content was elevated and gluconeogenesis was reduced, whereas glycolysis was not activated. In oncocytomas glycogen was not detected and glucose-6-phosphate dehydrogenase, pyruvate kinase, and fructose-1,6-diphosphatase activities remained unchanged. CONCLUSIONS: It has been demonstrated that a series of characteristic changes occur in the carbohydrate metabolism of renal clear cell carcinomas: glycogen and glucose-6-phosphate levels increase, glycolysis is activated, and gluconeogenesis is reduced. Furthermore, the alterations of the carbohydrate metabolism within clear cell carcinomas are clearly distinct from those observed in chromophilic cell carcinomas, chromophobe cell carcinomas, and oncocytomas.     

Chronic effects of clozapine administration on insulin resistance in rats: Evidence for adverse metabolic effects

Chronic treatment with the atypical antipsychotics clozapine has been associated with an increased risk for deterioration of glucose homeostasis, leading to hyperglycemia and insulin resistance diabetes. The present study mainly aimed to investigate possible mechanisms underlying clozapine-induced hyperglycemia. Male Wistar albino rats were randomly divided into two groups (each consists of 12 rats). The first group received clozapine orally at a dose of 10 mg/kg body weight daily for 6 weeks, while the other group received the drug vehicle only and served as the control group. At the end of the six weeks, hyperglycemia, hyperinsulinemia and insulin resistance, as indicated by Homeostatic model assessment of insulin resistance (HOMA-IR), were observed in the clozapine group as compared with the control group. This disturbance in glucose regulation was associated with non-significant changes in body weight, serum cortisol level, and hepatic glycogen content. The Clozapine group showed a significant increase in hepatic phosphorylase activity and in the gene expression level of hepatic glucose-6-phosphatse (G6Pase) enzymes compared to the control group. It can be concluded that clozapine-induced hyperglycemia and insulin resistance occur in a manner mostly independent of weight gain, and may be attributed to an increase in hepatic phosphorylase activity and increased expression level of G6Pase.     

Serum and hepatic enzyme activity in rats treated with diethylnitrosamine

Comparative studies of enzyme activities during the dedifferentiation of hepatic cells and through their development into overt hepatomas are few and contradictory. This study was designed to investigate the histochemical, biochemical and morphologic features of the altered liver cells with particular emphasis on the importance and validity of the histoenzymatic behavior of glucose-6-phosphatase (G6Pase) as a marker for the detection of precancerous hepatic cells. Serum and hepatic levels of G6Pase were analyzed and compared with the histoenzymatic behavior of this enzyme. The use of other enzymes, such as adenosine triphosphatase (ATPase) and gamma glutamyl-transpeptidase (GGT) as histochemical markers for malignancy was also tested. The activities of a variety of enzymes commonly used as diagnostic tools were also evaluated in both the liver homogenates and sera of rats treated with 2 mg diethylnitrosamine (DENA)/kg body weight for 2-28 weeks. Using G6Pase as a histoenzymatic marker, precancerous cells appeared after 4 weeks of exposure to DENA in the form of small islets devoid of G6Pase activity. These G6Pase free cells increased in number forming larger islands and finally appeared as tumor nodules after 28 weeks of treatment. The histoenzymatic behavior of ATPase was identical to that of G6Pase. The precancerous cells, as well as the tumor cells appeared devoid of ATPase activity. The application of GGT as a marker, showed significantly increased activity in the altered liver and tumor cells. Increased serum levels of G6Pase were noted after 10 weeks and were greatly elevated in the late stages of the evolution of the precancerous cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Glycogen storage disease type 1a in Israel: Biochemical,clinical, and mutational studies

Glycogen storage disease type 1a (von Gierke disease, GSD 1a) is caused by the deficiency of microsomal glucose-6-phosphatase (G6Pase) activity which catalyzes the final common step of glycogenolysis and gluconeogenesis. The recent cloning of the G6Pase cDNA and characterization of the human G6Pase gene enabled the characterization of the mutations causing GSD 1a. This, in turn, allows the introduction of a noninvasive DNA-based diagnosis that provides reliable carrier testing and prenatal diagnosis. In this study, we report the biochemical and clinical characteristics as well as mutational analyses of 12 Israeli GSD 1a patients of different families, who represent most GSD 1a patients in Israel. The mutations, G6Pase activity, and glycogen content of 7 of these patients were reported previously. The biochemical data and clinical findings of all patients were similar and compatible with those described in other reports. All 9 Jewish patients, as well as one Muslim Arab patient, presented the R83C mutation. Two Muslim Arab patients had the V166G mutation which was not found in other patients' populations. The V166G mutation, which was introduced into the G6Pase cDNA by site-directed mutagenesis following transient expression in COS-1 cells, was shown to cause complete inactivation of the G6Pase. The characterization of all GSD 1a mutations in the Israeli population lends itself to carrier testing in these families as well as to prenatal diagnosis, which was carried out in 2 families. Since all Ashkenazi Jewish patients harbor the same mutation, our study suggests that DNA-based diagnosis may be used as an initial diagnostic step in Ashkenazi Jews suspected of having GSD 1a, thereby avoiding liver biopsy. Am. J. Med. Genet. 72:286–290, 1997. © 1997 Wiley-Liss, Inc.     

Glycogen-forming function of hepatocytes in cirrhotically altered rat liver after treatment with chorionic gonadotropin

Using cytofluorimetric and biochemical studies on serial supravital liver punctate biopsies, effects of chorionic gonadotropin (CG) on recovery of hepatocyte glycogen-forming function in the cirrhotically altered rat liver were analyzed. The biopsies were taken first from rats with experimental cirrhosis produced by their 6-month-long poisoning with the hepatotoxic poison CCl4, then from the same animals in 1, 3, and 6 month after cessation of their poisoning, either on treatment with CG or with no treatment. In smears of isolated hepatocytes, the contents of the total glycogen (TG) and of its labile and stable fractions (LF and SF, respectively) were measured. In liver homogenates, activities of glucose-6-phosphatase (G6Pase), glycogen phosphorylase, and glycogen synthetase were determined. It was found that the threefold increased TG content in hepatocytes of cirrhotic liver returned to the normal level in 3 months without treatment, while as soon as in 1 month in the case of the treatment with CG. The CG treatment for 3 months resulted in normalization of the glycogen fraction composition that had been changed in cirrhotic liver, whereas without treatment, the glycogen LF/SF ratio remained changed even after 6 months after cessation of the poisoning with CCl4. Activity of G6Pase was fourfold reduced in cirrhosis; in 3 months after the end of poisoning, under effect of CG, the activity increased to the normal level, but somewhat decreased subsequently. In the animals that were not treated with CG, the decrease in the G6Pase activity after the cessation of the CCl4 poisoning was even more marked than in the CG-treated rats. Activities of two other enzymes of glycogen metabolism did not differ statistically significantly from the norm throughout the entire experiment. The data obtained indicate that the use of CG for rehabilitation of the glycogen-forming function of the cirrhotically altered liver is more efficient than other ways of treatment studied previously, such as partial hepatectomy or a high-carbohydrate diet.     

Identification of mutations in the glucose-6-phosphatase gene in Czech and Slovak patients with glycogen storage disease type ia, including novel mutations K76N, V166A and 540del5

Mutations in the glucose-6-phosphatase (G6Pase) gene are responsible for glycogen storage disease type Ia (GSD Ia). A study of the molecular basis of GSD Ia was carried out in 12 Czech and Slovak GSD Ia patients from 10 unrelated families. Mutation analysis was performed for the entire coding region of G6Pase gene using DGGE, sequencing and PCR/digestion. With the strategy used, all mutant alleles were identified in this study. Three novel mutations (K76N, V166A and 540del5), six previously described mutations (W77R, R83C, G188R, R295C, Q347X and 158delC) and one known polymorphism (1176T-->C) were detected. The most common mutation identified was R83C, accounting for 8 out of 20 (40%) mutant alleles. The K76N mutation was found in a Gypsy family: two siblings with GSD Ia were homozygous for this mutation. These findings expand our knowledge of mutations responsible for glycogen storage disease type Ia.     

Glycogen storage disease type Ia: Four novel mutations (175delGG,R170X,G266V and V338F) identified

Deficient activity of glucose‐6‐phosphatase (G6Pase) causes glycogen storage disease type Ia (GSD Ia). We analysed the G6Pase gene of 16 GSD Ia patients using single strand conformation polymorphism (SSCP) analysis prior to automated sequencing of exon(s) revealing an aberrant SSCP pattern. In all GSD Ia patients we were able to identify mutations on both alleles of the G6Pase gene, indicating that this method is a reliable procedure to identify mutations. Four novel mutations (175delGG, R170X, G266V and V338F) were identified. © 1998 Wiley‐Liss, Inc.     

Control of glycogen metabolism in the developing turkey poult.

An experiment was conducted with young turkey poults to evaluate factors controlling glycogen metabolism in the period following hatching. Glucose and sucrose solutions were given along with a standard starter diet. Liver and carcass glycogen were measured on days 1, 4 and 6. Liver glycogen synthetase (EC 2.4.1.21) and phosphorylase (EC 2.4.1.1) were also assayed at these times. The characteristics of active and inactive glycogen synthetase at these times were determined and sensitivity of the active and inactive forms were related to physiological concentrations of glucose-6-phosphate. Supplemental glucose or sucrose increased carcass glycogen in comparison to controls; however, but sucrose was more effective than glucose in promoting liver glycogen synthesis in 4- and 6-day-old poults. There was an age dependent increase in carcass glycogen between days 1 and 6, but a decrease in liver glycogen between days 4 and 6. The activation of liver glycogen synthetase is incomplete in 1 day old poults but activity increases during the 1st week of life. Activation of glycogen synthetase decreased the apparent Ka for glucose-6-phosphate. Phosphorylase inactivation in vitro was not affected by age. Liver glucose-6-phosphate increases rapidly after hatching and the concentration is related to the in vitro Ka derived for both active and inactive synthetases. Both glucose and sucrose increased liver glucose-6-phosphate at days 4 and 6 as well as glycogen synthetase activity. The increase in enzyme activity may be caused indirectly by an allosteric effect of glucose-6-phosphate. Phosphorylase, while not affected by supplemental carbohydrates, did decrease in activity between days 4 and 6. The decrease in activity could affect the phosphorylase a/ synthetase a ratio and change glycogen metabolism.     

The development of functional heterogeneity in the liver parenchyma of the golden hamster

Summary Prenatal and postnatal stages of the development of golden hamsters were studied histochemically and biochemically. It was shown that, beginning with the 12^th gestational day, the fetal liver starts to store glycogen, and that this process reaches its maximum a birth. Glycogen phosphorylase and glucose-6-phosphatase (G6Pase)-activity increased drastically in the last two days before birth, glycogen phosphorylase preceding G6Pase. As a histochemical characteristic, an even distribution of glycogen, glycogen phosphorylase and G6Pase activity is found in the liver parenchyma at birth. During the first two postnatal weeks typical heterogeneous patterns of distribution developed: glycogen depletion could be demonstrated predominantly in zone 1 of the liver acinus, this being at the same time the area of highest glycogen phosphorylase and G6Pase-activity. The periportal zone 1 thus became characterized as the primary site of glycogenolysis (glycogen phosphorylase) and gluco(neo)genesis (G6Pase). Metabolic Zonation is interpreted as the chemomorphological equivalent of the regulatory function of the liver as a glucostat.Dedicated to Prof. Dr. A.M. Rappaport on the occasion of his 75th birthday, with sincere thanks for many years of fruitful discussionSupported by a grant from the SFB 46 (Molgrudent)