Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01275 (glucagon)
 26,492 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The purpose of such studies is to identify the hormones that act on the developmental formation of individual urea cycle enzymes, namely argininosuccinate synthetase, argininosuccinate lyase and arginase in the rat fetal liver. The development of argininosuccinate synthetase activity which is completely blocked by the suppression of glucocorticoids in the fetal liver is affected by neither glucagon nor thyroxine. The activity of argininosuccinate lyase which is never changed by the suppression or addition of glucocorticoids, is under the influences of glucagon and thyroxine at a late fetal period and the enzyme activity can be precociously induced in utero by injection of dibutyryl cyclic AMP to fetuses. Cortisol has been shown to precociously stimulate fetal liver arginase activity after an intraperitoneal injection, but the rise in activity at the late fetal period is not completely prevented by suppression of glucocorticoid and it seems that glucagon and thyroxine may also promote its developmental formation just before birth.
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PMID:Hormonal regulation of three urea cycle enzymes in rat fetal liver. 21 56

Parenchymal cells from adult rat liver, cultured in perifused monolayers, increased the levels of urea-cycle enzymes between 15% and 60% in response to glucagon within 24 h. This stimulation was drastically enhanced by the simultaneous presence of dexamethasone, especially in the case of argininosuccinate synthetase and argininosuccinate lyase, which increased nearly threefold. Dexamethasone itself produced only negligible stimulation, but exerted a similar effect on the stimulatory action of glucagon, if it was exclusively present during 6 h prior to the glucagon treatment, suggesting a permissive action of this hormone. The effect of glucagon, particularly in the presence of dexamethasone, was mimicked by dibutyryl adenosine 3':5'-monophosphate, whereas epinephrine was ineffective. All stimulations induced by hormones or dibutyryl adenosine 3':5'-monophosphate were abolished by cycloheximide, suggesting the involvement of protein synthesis in the induction process. Using the usual culture technique with a discontinuous supply of medium no significant effect of glucagon and dexamethasone could be measured. This striking difference between both culture systems indicates that perifusion is the more adequate in vitro system for studies of the regulation of enzyme levels. Possible reasons for the failure of hormonal stimulation of urea-cycle enzymes in normal monolayer culture are discussed.
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PMID:Permissive effect of dexamethasone on glucagon induction of urea-cycle enzymes in perifused primary monolayer cultures of rat hepatocytes. 47 71

Adrenalectomized and intact rats were given constant high-dose infusions of glucagon, 0.3 mg/kg per day for 7 days, with or without low-dose dexamethasone, 0.01 mg/kg daily, to test whether glucocorticoids potentiate glucagon induction of the 5 urea cycle enzymes as they do in cultured rat hepatocytes. Glucagon did not induce any of the urea cycle enzymes in adrenalectomized Sprague-Dawley rats and only induced argininosuccinate lyase (EC 4.3.2.1) in adrenalectomized inbred Wistar-Furth rats. Dexamethasone alone induced arginase in adrenalectomized and in intact Wistar-Furth rats and restored the other enzymes to normal levels in adrenalectomized rats. In intact Wistar-Furth rats, the combination of hormones gave synergistic increases of all 5 enzymes over the responses to each hormone alone, but in adrenalectomized rats the combination was only additive or less than additive compared with the sum of single hormone responses. The lack of synergism between the two hormones in adrenalectomized rats suggest that other factors play a role in glucagon induction of this cycle.
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PMID:Dexamethasone and glucagon cause synergistic increases of urea cycle enzyme activities in livers of normal but not adrenalectomized rats. 180 64

Foetal-rat hepatocytes were cultured in primary monolayer culture, and activity changes of argininosuccinate synthetase (ASS, EC 6.3.4.5) and argininosuccinase (ASL, EC 4.3.2.1) were followed under defined hormone conditions. In hormone-free medium, cultured cells maintained the enzyme activities at values equal to those of freshly isolated cells for at least 3 days. Continuous addition of dexamethasone produced the development of the two enzyme activities, but only after the first 20h of culture. Under these conditions, urea production by the foetal hepatocytes was concomitantly increased in the culture medium. Pretreatment with dexamethasone for 20h was sufficient to produce the development of ASL activity within the 2 following days. Introduced alone, glucagon induced an increase of ASL activity, but did not affect the ASS activity. The most powerful stimulation of ASS and ASL could be observed in cultured hepatocytes if glucagon and dexamethasone were added simultaneously or sequentially. These results indicated that the development of the receptor complex for the induction of urea-cycle enzymes appears early before birth and established that glucocorticoids amplify the glucagon stimulation of these enzyme activities during foetal life.
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PMID:Hormonal regulation of two urea-cycle enzymes in cultured foetal hepatocytes. 666 Nov 96

During the perinatal period, the activity of the urea-cycle enzyme argininosuccinate lyase (ASL) is regulated by glucocorticoids, glucagon and insulin. In this study, the effects of glucagon and cyclic AMP (cAMP) analogues were examined on the synthesis of ASL and on the level of its corresponding mRNA in cultured foetal hepatocytes. Northern-blot analysis revealed that these agents only gave a transient induction of ASL mRNA amount, which reached a peak at 6 h and declined thereafter. This induction preceded the increase in enzyme activity and amount which could be observed for 2 or 3 days of culture. Stimulation of ASL mRNA accumulation by a combination of cAMP analogues and dexamethasone was additive, indicating that glucocorticoids and cAMP are both necessary to promote hepatocyte differentiation and that inductions could occur via independent pathways. Induction by cAMP analogues could be abolished by actinomycin D, suggesting a control mechanism at the transcriptional level. Puromycin was without effect on ASL mRNA induction by cAMP, indicating that no ongoing protein synthesis was required in the stimulation process.
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PMID:Changes in levels of argininosuccinate lyase mRNA during induction by glucagon and cyclic AMP in cultured foetal-rat hepatocytes. 838 74

The gene of argininosuccinate lyase (ASL) is expressed in a developmental specific manner in the liver and is regulated by hormones, namely glucocorticoids, glucagon and insulin. To assess the role of DNA methylation in the developmental pattern of ASL gene expression, we analyzed the restriction profile obtained by cleavage of genomic DNA with MspI and HpaII in fetal and adult rat liver, two developmental stages with different levels of expression of the ASL gene. Southern analysis showed that the 5' region of this gene appeared more methylated in the fetal liver which expressed ASL at a low level than in the adult liver where the ASL gene is highly expressed. Moreover, treatment of fetuses of various gestational stages with the hypomethylating agent 5-azacytidine for 18 h caused an increase of the hepatic ASL activity and mRNA level. The stimulating effect of this drug could be also observed in vitro in cultured fetal hepatocytes. These results suggest a developmental control of the ASL gene by the DNA methylation status.
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PMID:Developmental control of argininosuccinate lyase gene by methylation. 953 37

Urea is an important reutilizable nitrogen source for the ruminant and is mainly synthesized through the urea cycle in the liver. The cycle is undertaken by 5 enzymes: carbamoyl phosphate synthetase (CPS), ornithine transcarbamoylase (OTC), arginino-succinate synthetase (AS), argininosuccinate lyase (AL), and arginase. The purpose of this study was to investigate changes in the activity of the enzymes and mRNA expression, given that previous observations have indicated an increase in plasma urea concentrations with age in Holstein calves. First, plasma concentrations of metabolites and hormones were determined in calves at 1, 3, 8, 13, and 19 wk of age (n = 4, weaned at 6 wk of age). The plasma concentration of urea drastically increased after weaning (P < 0.001). The plasma concentration of glucose was lowest at 8 wk. The plasma concentration of IGF-I gradually increased with age, although those of NEFA, glucagon, and cortisol decreased (P < 0.001). Concentrations of triglyceride, alpha-amino nitrogen, growth hormone, and insulin did not change significantly with age of the calf. Next, using the liver tissues taken from calves at 2, 13, and 19 wk of age (n = 4 to 6 at each time point, weaned at 6 wk of age), we measured the activity and mRNA expression of the enzymes by biochemical methods and quantitative reverse transcription-PCR, respectively. The activities of CPS (P < 0.001), OTC (P = 0.001), and AS (P = 0.015) increased with age, whereas AL (P = 0.003) decreased. Although mRNA expression was decreased with age for AL (P = 0.002) and arginase (P = 0.007), no significant change was observed for CPS, OTC, or AS mRNA expression. We conclude that the increased urea production in the liver may be explained not only by an increase in the activities of the urea cycle enzymes, but also by increased ammonia production by rumen fermentation and gluconeogenesis from amino acids around weaning time.
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PMID:Changes of activity and mRNA expression of urea cycle enzymes in the liver of developing Holstein calves. 1834