Role of Glucocorticosteroid Hormones on the Levels of Rat Liver Carbamoylphosphate Synthase (Ammonia) and Arginase Activity during Ontogenesis

Lamers, W. H.; Mooren, P.G.

doi:10.1159/000241264

Cited by 40 publications

(27 citation statements)

References 5 publications

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“…Note the different scales on they axis. the decrease in liver wet weight after natural birth is due to the loss of glycogen and protein (29)(30)(31)(32)45). Therefore, the 25% decrease in cell volume in glucose-supplemented fetuses, relative to the fetuses taken directly after caesarian section, occurs also after natural birth.…”

Section: Effects Of Short-term Starvationmentioning

confidence: 99%

Changes in Hepatic Nitrogen Balance in Plasma Concentrations of Amino Acids and Hormones and in Cell Volume after Overnight Fasting in Perinatal and Adult Rat

et al. 1995

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ARSTRImportant regulatory factors of intrahepatic protein synthesis and proteolysis are amino acids, glucagon, insulin, and cell volume. We have investigated the changes in these factors with development and after an overnight fast and evaluated their contribution to changes in the hepatic nitrogen balance in vivo. In the fed state, glucagon levels were highest in suckling animals and gradually declined in older rats, whereas the concentration of insulin increased during development. The amino acid concentrations in liver and plasma declined during the suckling period to levels that in vitro are highly permissive for induction of autophagic proteolysis. In all age groups investigated, fasting was associated with a drop in hepatic protein content, together with a marked decrease in hepatocellular volume and insulin concentrations. On the other hand, glucagon concentrations and the concentration of many amino acids in plasma and liver responded to fasting with a pronounced decrease in perinatal and suckling animals, but this response had become blunted at weaning and had disappeared in adult animals. These findings suggest that insulin and/or hepatocellular volume are more likely candidates as short-term physiologic regulators of the hepatic nitrogen balance than are glucagon or amino acids. In glucosesupplemented fetuses, high levels of insulin could not compensate for a decreased hepatocellular volume in averting a catabolic state, suggesting that cell volume is the more important factor. Although our study cannot discriminate between the effects of fasting on protein synthesis and degradation, our findings show unequivocally that, for a rapid growth of the liver, suckling animals have to be fed around-the-clock. (Pediatr Res 38: 1018-1025, 1995)The cellular protein content is regulated by modulation of the rates of synthesis and/or degradation. The nutritional and hormonal status have been shown to be of paramount importance as modulators of the rate of synthesis and degradation of proteins in the liver (1-7). In vivo studies in which the effect of refeeding after prolonged periods of starvation (2-5 d) was studied (8-10) and in vitro studies with perfused livers (cf. Ref. I), freshly isolated (6,7,11,12) or cultured hepatocytes (13-15) have identified amino acids and the hormones insulin and glucagon as major determinants of hepatic lysosomal proteolysis and protein synthesis. High ambient concentrations of amino acids and insulin suppress intrahepatic proteolysis (1, 6, 7) and stimulate protein synthesis (16-19), whereas glucagon exerts the opposite effect (1,13,14,20). More recently, it was proposed that lysosomal proteolysis in rat liver is also regulated by changes in the volume of the hepatocyte, an increase in cell volume being inhibitory (21, 22). As indicated, most of these findings were obtained from in vitro studies, involving strong manipulation of the nutritional and hormonal environment of the hepatocytes. In this respect, we had previously observed in cultured hepatocytes that intrahepatic lysoso...

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Section: Effects Of Short-term Starvationmentioning

confidence: 99%

Changes in Hepatic Nitrogen Balance in Plasma Concentrations of Amino Acids and Hormones and in Cell Volume after Overnight Fasting in Perinatal and Adult Rat

et al. 1995

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“…1). A similar increase in the accumulation of enzyme is also found in vivo in the prenatal period and was explained by a recruitment of previously inactive hepatocytes for enzyme synthesis [27]. Immunocytochemical staining of fetal liver sections has since supported this explanation [28].…”

Section: Discussionmentioning

confidence: 56%

Synthesis, accumulation and turnover of carbamoylphosphate synthetase and phosphoenolpyruvate carboxykinase in cultures of embryonic rat hepatocytes

Roon

Charles

Lamers³

1987

European Journal of Biochemistry

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Glucocorticosteroid, thyroid hormones and cyclic AMP can induce the synthesis of carbamoylphosphate synthetase and phosphoenolpyruvate carboxykinase in cultures of hepatocytes as soon as these cells differentiate from the embryonic foregut. The low levels of both enzymes that can accumulate in such still protodifferentiated hepatocytes are due to low levels of enzyme synthesis. In cultures, the rate of synthesis of both enzymes increases continually in the presence of hormones, showing that maturation of the capacity for synthesis towards the postnatal, fully differentiated situation is occurring in these cells. The turnover rate of both enzymes in embryonic hepatocytes is lower in the presence of hormones than in the absence, but does not change during the culture period. In the presence of hormones the turnover rate is comparable to that found in adult rat liver in vivo. The development of the capacity to accumulate organ-specific enzymes in vitro (and hence the rate of enzyme synthesis) is found to be comparable to that in utero.During rat-liver development several hepatocyte-specific proteins become enzymatically detectable upon the completion of liver organogenesis. However, in the presence of glucocorticosteroids, triiodothyronine and cyclic AMP, the accumulation of the urea-cycle enzyme carbamoylphosphate synthetase and the gluconeogenic enzyme phosphoenolpyruvate carboxykinase can already be demonstrated in monolayer cultures of hepatocytes at the beginning of the organogenetic period, i.e. from the moment hepatocytes become recognizable [l, 21. The experiments further indicated that the capacity of these cells to accumulate hepatocytespecific enzymes is still limited [l], even when cultured in an optimized medium [2].The capacity to accumulate proteins is determined by the balance of the rate of protein synthesis and the rate of protein degradation. There is general agreement that in perinatal rat liver, rates of protein synthesis are relatively high and rates of protein degradation are relatively low compared to those in the adult liver [3 -51. In this period a rapid accumulation of many hepatocyte-specific enzymes is observed. Such reciprocal changes in the rates of protein synthesis and degradation have also been demonstrated for specific proteins, e.g. phosphoenolpyruvate carboxykinase [6], and may reflect the general mechanism for the rapid accumulation of specific protein during terminal differentiation of cells [7].In view of these observations, it seemed possible that the observed low capacity of embryonic hepatocytes to synthesize organ-specific proteins [l] reflects their still protodifferentiated state of development [8]. This hypothesis predicts an increase in the synthetic capacity of the (cultured) hepatocytes upon further development towards the differentiated state.

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“…The preparation of the tissue, the enzyme assays, the protein and the deoxyribonucleic acid estimates were as described previously (40). All values referred to in the graphs and text were obtained from at least two litters and 2 -4 preparations per litter, and depicted or expressed as means ± SD.…”

Section: Hormonesmentioning

confidence: 99%

“…In a previous paper (40) it was shown that daily administration of synthetic glucocor ticosteroid hormones resulted in only a faint stimulation of carbamoylphosphate synthase and arginase activities in the prenatal period compared to the postnatal period (see also : 16).…”

Section: Introductionmentioning

confidence: 98%

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Role of Thyroid Hormones in the Normal and Glucocorticosteroid Hormone-Induced Evolution of Carbamoylphosphate Synthase (Ammonia) and Arginase Activity in Perinatal Rat Liver

Lamers¹,

Mooren²

1980

Neonatology

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Administration of thyroid hormones causes a dose-dependent increase in carbamoylphosphate synthase (ammonia) and arginase activities in fetal rat liver but not in neonatal rat liver. Simultaneous administration of thyroid and glucocorticosteroid hormones enhances enzyme accumulation still further in the fetus. When administered before birth, the relative potencies of T₄ and reverse T₃, compared to T₃ are 20–25% and 1–2%, respectively. Both before and after birth, thyroid hormones enhance DNA content of the liver. Hypophysectomy of rat fetus reduces the carbamoylphosphate synthase activity level in hepatocytes to 30–40% of that in intact animals. Thyroid and glucocorticosteroid hormone administered individually to hypophysectomized animals stimulate enzyme activity 2- to 3-fold; and if administered simultaneously, 4- to 6-fold. Premature delivery with continuation of thyroid and/or glucocorticosteroid hormone treatment started before birth shows uninterrupted enzyme accumulation profiles. Delaying birth by progesterone treatment of the dam leads to uninterrupted but reduced rates of enzyme accumulation in hepatocytes.

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Role of Glucocorticosteroid Hormones on the Levels of Rat Liver Carbamoylphosphate Synthase (Ammonia) and Arginase Activity during Ontogenesis

Cited by 40 publications

References 5 publications

Changes in Hepatic Nitrogen Balance in Plasma Concentrations of Amino Acids and Hormones and in Cell Volume after Overnight Fasting in Perinatal and Adult Rat

Changes in Hepatic Nitrogen Balance in Plasma Concentrations of Amino Acids and Hormones and in Cell Volume after Overnight Fasting in Perinatal and Adult Rat

Synthesis, accumulation and turnover of carbamoylphosphate synthetase and phosphoenolpyruvate carboxykinase in cultures of embryonic rat hepatocytes

Role of Thyroid Hormones in the Normal and Glucocorticosteroid Hormone-Induced Evolution of Carbamoylphosphate Synthase (Ammonia) and Arginase Activity in Perinatal Rat Liver

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