Developmental expression of glycogenolytic enzymes in rabbit tissues: possible relationship to fetal lung maturation

Newgard, Christopher B.; Norkiewicz, Brian; Hughes, Steven D.; Frenkel, René; Coats, Ward; Martiniuk, Frank; Johnston, John M.

doi:10.1016/0167-4781(91)90198-u

Cited by 11 publications

(9 citation statements)

References 40 publications

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“…In isolated adult rat hepatocytes, fructose binding regions of human and rabbit brain phosphorylase have activates both glycogen synthase and glycogen phosphorylase been mapped and do not differ from muscle and liver phospho- (26). Further, activation of glycogen synthase by glucose is im-rylase (45). Further, in both human and rabbit fetal liver tissues, paired if glucose 6-phosphate levels are lowered, but phospho-it has not been possible to confirm a predominant "fetal phosrylase is inactivated normally (27).…”

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confidence: 99%

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Glycogenesis in the Cultured Fetal and Adult Rat Hepatocyte Is Differently Regulated by Medium Glucose

et al. 1992

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confidence: 99%

“…Further, in both human and rabbit fetal liver tissues, paired if glucose 6-phosphate levels are lowered, but phospho-it has not been possible to confirm a predominant "fetal phosrylase is inactivated normally (27). phorylase" using molecular cloning techniques (45,46). A third…”

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confidence: 99%

Glycogenesis in the Cultured Fetal and Adult Rat Hepatocyte Is Differently Regulated by Medium Glucose

et al. 1992

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“…In the fetus, an increase followed by a decrease in total lung and type II epithelial cell glycogen has been observed in mouse [20], hamster [25], rat [26][27][28][29][30], and rabbit [31][32][33]. It has been shown that lung glycogen breakdown provides glucose for fatty acid and glycerol synthesis which in turn are incorporated into surfactant phospholipids in the type II cells, and a direct precursor-product relationship has indeed been established [34].…”

Section: Discussionmentioning

confidence: 99%

Effect of Prenatal Glucocorticoid on Fetal Lung Ultrastructural Maturation in hyt/hyt Mice with Primary Hypothyroidism

Ansari

Mello²,

Devaskar³

1999

Neonatology

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Glucocorticoids (GC) and thyroid hormones (TH) accelerate fetal lung maturation. Though GC are used clinically, the mechanisms of GC-induced fetal lung maturity remain unclear. Prenatal GC increase fetal TH activity in humans and in animals. Thus, it is possible that increased fetal TH activity after prenatal GC plays a role in accelerating fetal lung maturation. However, this hypothesis has remained untested due to the lack of a suitable animal model. In the hyt/hyt mouse primary hypothyroidism occurs due to a point mutation in the beta subunit of the thyroid-stimulating hormone receptor of the thyroid gland, and it is transmitted in an autosomal recessive manner. We studied the effect of maternal betamethasone on fetal lung ultrastructure in hyt/hyt (hypothyroid) and Balb-c (euthyroid) mice. Hypothyroid mice were made euthyroid by T₃ supplementation and mated to carry hypothyroid pups. Vehicle (n = 6) or betamethasone (n = 6) was injected intraperitoneally twice daily into the doe on days 16 and 17 of gestation. Fetal lungs on 18 days of gestation were subjected to ultrastructural morphometric analysis. The number of lamellar bodies per type II cell increased after betamethasone in Balb-c (2.10 ± 0.31 vs. 3.43 ± 0.37) and hyt/hyt (0.77 ±0.28 vs. 3.85 ± 0.26) mice. The alveolar-to-parenchymal ratio was less in the vehicle-treated hyt/hyt (0.082 ± 0.024) as compared with the vehicle-treated Balb-c (0.30 ± 0.05) mice, while prenatal betamethasone increased the alveolar-to-parenchymal ratio in the hyt/hyt (0.227 ± 0.034) but not in the Balb-c (0.26 ± 0.04) mice. The glycogen-to-nucleus ratio was higher in betamethasone-treated hyt/hyt mice (1.46 ± 0.20) when compared to vehicle-treated hyt/hyt (0.89 ± 0.14) or Balb-c (1.01 ± 0.17) or betamethasone-treated Balb-c (0.81 ± 0.13) mice. Though tubular myelin was readily apparent in the airspace lumen of betamethasone-treated Balb-c mice, it was absent in betamethasone-treated hyt/hyt fetal lungs. We conclude that fetal thyroid plays an important role in accelerating some aspects of fetal lung ultrastructural maturation from GC stimulation.

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“…Glycogen phosphorylase enzyme activity has been shown to increase in late gestation fetal lung concomitant with initiation of glycogen degradation (5). In contrast to the developmentally regulated increase in enzyme activity, the level of RNA encoding brain glycogen phosphorylase, the predominant isoform of glycogen phosphorylase in developing rabbit lung, does not change during the perinatal period (6), suggesting that enzyme activity is regulated by allosteric activation and/or by post-translational phosphorylation. Activation of glycogen phosphorylase by phosphorylation is regulated by phosphorylase kinase (PhK).…”

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confidence: 88%

The Testis Isoform of the Phosphorylase Kinase Catalytic Subunit (PhK-γT) Plays a Critical Role in Regulation of Glycogen Mobilization in Developing Lung

Liu

Rannels

Falconieri

et al. 1996

Journal of Biological Chemistry

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In order to identify the form of phosphorylase kinase catalytic subunit expressed in developing lung, degenerate polymerase chain reaction primers were designed based on conserved domains of the two known catalytic subunits, expressed primarily in muscle and testis. Amplification of cDNA from day 19 fetal rat lung followed by cloning and sequence analyses indicated that only the testis isoform of phosphorylase kinase (PhK-␥T) was detectable in fetal lung. In situ hybridization analyses indicated that expression of PhK-␥T RNA in developing lung tissue was widespread and not restricted to Type II epithelial cells; PhK-␥T protein expression was temporally and spatially correlated with expression of PhK-␥T RNA. PhK-␥T RNA and protein expression was also characterized in the PhK-deficient glycogen storage disease (gsd) rat. PhK-␥T RNA levels were similar in Type II cells isolated from wild type and gsd/gsd fetuses; in contrast, PhK-␥T protein was virtually undetectable in gsd/ gsd Type II cells and enzyme activity was very low. These results suggest that PhK-␥T plays a critical role in mobilization of glycogen during fetal lung development and that failure to catabolize glycogen in the gsd/gsd rat is related to an untranslatable PhK-␥T RNA or unstable protein.

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Developmental expression of glycogenolytic enzymes in rabbit tissues: possible relationship to fetal lung maturation

Cited by 11 publications

References 40 publications

Glycogenesis in the Cultured Fetal and Adult Rat Hepatocyte Is Differently Regulated by Medium Glucose

Glycogenesis in the Cultured Fetal and Adult Rat Hepatocyte Is Differently Regulated by Medium Glucose

Effect of Prenatal Glucocorticoid on Fetal Lung Ultrastructural Maturation in hyt/hyt Mice with Primary Hypothyroidism

The Testis Isoform of the Phosphorylase Kinase Catalytic Subunit (PhK-γT) Plays a Critical Role in Regulation of Glycogen Mobilization in Developing Lung

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