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)

An injection of cortisone acetate at a dose of 5 mg/100 g body weight concomitant with dibutyryl cyclic AMP prevents the increase in the activity of rat liver cytosol serine aminotransferase (L-serine:pyruvate aminotransferase, EC 2.6.1.51) elicited by the nucleotide with a lag of about 2 h. If the glucocorticoid is given 2 h prior to the nucleotide inducer, the lag disappears. The inhibitory effect of cortisone acetate gradually decays and is no longer detectable 12 h following its administration. Theophylline, insulin and glucose at doses which affect significantly the level of tyrosine aminotransferase, have not effect on the level of serine aminotransferase and on the cortisone inhibition. The inhibitory effect of the glucocorticoid on the dibutyryl cyclic AMP-mediated increase in serin aminotransferase diminishes with the age of animall. Increases in the enzyme activity by a single dose of glucagon can also be inhibited by cortisone acetate and actinomycin D as in the case with dibutyryl cyclic AMP as an inducer. The possibility of the existence of a specific inhibitory factor which is formed in response to cortisone acetate is discussed.
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PMID:Inhibitory effect of cortisone acetate on the stimulation of rat liver cytosol L-serrine. Pyruvate aminotransferase by dibutyryl adenosine 3,5-monophosphate. 16 60

We have studied glucagon induction of enzymes, adenosine 3', 5'-monophosphate concentrations, and glucose repression in Morris 9618A hepatoma and in the liver of rats fed, for periods of up to 5 weeks, a solid diet containing 2-acetylaminofluorene or 3'-methyl-4-dimethylaminoazobenzene. While the basal levels of the enzymes serine dehydratase and tyrosine aminotransferase were the same as those found in control rats, their response to glucagon was reduced in experimental animals with or without tumors. However, the basal or glucagon-stimulated levels of adenosine 3', 5'-monophosphate in the liver of rats given the carcinogens were not changed. In Morris 9618A hepatoma, these parameters were, likewise, comparable to those in control animals. When glucose was administered to carcinogen-treated or tumor-bearing rats that had received a single dose of glucagon, there was no suppression of the increase in activity of serine dehydratase and tyrosine aminotransferase observed after glucagon treatment alone. The loss of glucose repression was seen already at 2 to 3 weeks following initiation of the carcinogenic diets. As previous studies had established for normal liver, the hormone-induced high levels of adenosine 3',5'-monophosphate remained unchanged also in Morris 9618A hepatoma and in rats given carcinogen. These results indicate that alterations in enzyme induction during chemical carcinogenesis are not the consequence of changes in adenosine 3',5'-monophosphate levels caused by carcinogens. The early disappearance of the glucose effect, which persists in slow-growing hepatomas, may be an expression of interference by carcinogens with the translation apparatus of the hepatic cell.
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PMID:Induction of enzymes by glucagon, glucose repression, adenosine 3',5'-monophosphate concentration during carcinogenesis and in Morris 6918A hepatoma. 23 92

DL-alpha-Methyltryptophan (alphaMeTrp), a synthetic analogue of tryptophan, has been found to be a potent inducer of hepatic tyrosine aminotransferase activity in the adrenalectomized rat. alphaMeTrp is inactive in vitro. Unlike the action of other known inducers (tryptophan, hydrocortisone, adenosine cyclic 3:5-monophosphate, and glucagon), maximal stimulation of enzyme activity occurs only 16 to 30 hours after alphaMeTrp administration and the activity is still elevated at 96 hours. Only the L isomer of alphaMeTrp is active, and addition of a hydroxyl group to position 5 of the indole ring renders an inactive compound. The induction can be prevented by actinomycin D or cycloheximide but not galactosamine. Administration of alphaMeTrp together with hydrocortisone produced an additive stimulation of enzyme activity. alphaMeTrp given along with glucagon or adenosine cyclic 3:5-monophosphate caused a further but not additive increase in enzyme activity. Tryptophan given along with alphaMeTrp promoted no extra stimulation whatsoever. These data indicate that alphaMeTrp and tryptophan may act via a common pathway which in part requires RNA synthesis. Other enzymes, namely alanine and aspartate aminotransferase, ornithine aminotransferase, ornithine carbamoyltransferase, serine dehydratase, and histidine ammonialyase, were not affected by treatment of rats with alphaMeTrp.
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PMID:Stimulation of tyrosine aminotransferase activity by dl-alpha-methyltryptophan. 23 76

1. In frog liver, tyrosine aminotransferase is located mainly in cytoplasm. The enzyme is an anionic protein of mol. wt. 115 000 daltons, specific toward 2-oxoglutarate. The enzyme separates on ion-exchange chromatography into two active forms. 2. Administration of triiodotyronine in vivo induces the activity of the enzyme. Epinephrine and glucagon have no effect, and cAMP and insulin repress this activity by about 70%. 3. Triiodotyronine stimulates incorporation of [14C]leucine into protein, and the amount of the enzyme in the nacent polysome-bound protein is considerably increased.
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PMID:Tyrosine aminotransferase in frog liver. 23 10

Liver explants from 20-day-old foetuses cultured for 48h in the absence of serum released 70% of their total soluble protein content into the medium. In the presence of serum this loss still amounted to 60%. The concentration of total particulate protein remained unchanged but there was some translocation of mitochondrial enzymes to the cytosol, and enzymes expected to increase during this stage of development failed to do so. The addition of cortisol plus glucagon (to serum-containing media) did not decrease the loss of total soluble protein from the explants but induced considerable tyrosine aminotransferase activity which was not released into the medium. The observations suggest that under the usual culture conditions a minority of the cells retain their functional integrity. The extent of deterioration, not reflected in histologically visible necrosis or cell damage, can be conveniently monitored by the malate dehydrogenase activity released to the medium.
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PMID:Biochemical changes in cultured foetal rat liver explants. 118 Sep 18

Hepatocytes were isolated from 17-day-old chick embryos by the use of collagenase. Glucagon and dibutyryl cAMP (bt2cAMP), individually or in combination, stimulated tyrosine aminotransferase (TAT) activity and synthesis in the isolated hepatocytes; maximal stimulation occurred 4 h after exposure of hepatocytes to the inducers. The stimulatory effects produced by glucagon and bt2cAMP were abolished by treatment of hepatocytes with cordycepin or cycloheximide. The effects of the hormone and the cyclic nucleotide were not additive. The induction of the enzyme by glucagon suggests a physiological role for the hormone in the expression of TAT activity during chick embryonic development.
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PMID:Effects of glucagon and an analogue of cAMP on tyrosine aminotransferase in isolated chick embryo hepatocytes. 135 57

Injection with pharmacological doses of dexamethasone (5 mg/kg) and/or bovine glucagon (1 mg/kg) exerts pronounced effects on toadfish liver compared with vehicle-treated control fish. Affected parameters include hepatic levels of glycogen and the activities of glutamate dehydrogenase, aspartate aminotransferase, malate dehydrogenase, and enzymes involved in NADPH generation as well as the kinetics of pyruvate kinase. Activities of tyrosine aminotransferase, however, a prime target for hormonal induction in mammals, remain unchanged in Opsanus. In subsequently isolated toadfish hepatocytes, metabolite concentrations and flux through gluconeogenesis are altered as are in vitro responses to epinephrine and catfish glucagon in previously injected fish. Contrary to existing mammalian models, short-term regulation of urea cycle activity can be ruled out for toadfish, since hormone treatments fail to influence the activity of two ornithine-urea cycle enzymes or the rate of hepatocyte-urea synthesis. Treatment-dependent increases in hepatic glutamine synthetase, the unique feeder enzyme for ammonia "nitrogen" in fish urea cycle, indicate a potentially pivotal role for this enzyme in longer-term regulation of ureogenesis.
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PMID:Metabolic actions of glucagon and dexamethasone in liver of the ureogenic teleost Opsanus beta. 160 Dec 63

Changes in the activities of pyruvate kinase, tyrosine aminotransferase and adenylate cyclase as well as in the number of alpha-1-adrenergic receptors of hepatocytes maintained in primary culture were investigated. During the culture in the presence of insulin and dexamethasone the activity of tyrosine aminotransferase (TAT) increased. The increase was suppressed by 12-O-tetradecanoylphorbol-13-acetate (TPA). The basic activity of adenylate cyclase increased; however, a weaker stimulation of the enzyme by glucagon was found. A loss of stimulation of pyruvate kinase by fructose-1,6-bisphosphate may result from phosphorylation of the enzyme. The number of alpha-1-adrenergic receptors decreased during culture, an event not influenced by TPA.
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PMID:Enzyme activities, isoenzyme pattern and alpha-1-adrenergic receptor number in primary cultured hepatocytes. 168 5

Multiple rounds of cell division were induced in primary cultures of rat hepatocytes in serum-free medium containing 10 mmol/L nicotinamide and 10 ng epidermal growth factor/ml. Cells per culture almost doubled between day 1 and day 5. The proliferating cells were predominantly mononucleate. The time course of DNA synthesis in cultured hepatocytes showed that peaks of the incorporation of 3H-thymidine were observed at 60 hr and 82 hr after plating. Labeling indices of the cells indicated that almost half the cells were labeled with 3H-thymidine in the periods 48 to 72 hr and 72 to 96 hr after plating. In addition, about 20% of the hepatocytes in culture initiated a second round of the cell cycle between 48 and 96 hr in culture, as demonstrated by the use of continuous treatments with 3H-thymidine and 5-bromo-2'-deoxyuridine. Furthermore, by day 4 of culture, about 40% and 15% of metaphases resulted from a second and third round of cell division, respectively. The cultured hepatocytes on day 5 stained with albumin immunocytochemically, and the activity of tyrosine aminotransferase was induced by dexamethasone and glucagon on day 3. In addition, electron micrographs revealed that dividing cells not only had many characteristics of liver mitochondria and bile canaliculus-like structures, but many also contained a few large peroxisomes with internal crystalline nucleoids.
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PMID:Multiple cell cycles occur in rat hepatocytes cultured in the presence of nicotinamide and epidermal growth factor. 182 39

Cultured rat hepatocytes have been used extensively to study the mechanisms of chemically induced peroxisome proliferation. Hepatocytes from nonrodent species have been used on a limited scale to study interspecies differences in the response. Because of their importance in pharmaceutical safety assessment, we have developed a model to study the response of beagle dog and rhesus monkey hepatocytes to peroxisome proliferators. Treatment of the hepatocytes with peroxisome proliferators was begun after 20 hr in culture and continued for 72 hr. Untreated rat, dog, and monkey hepatocytes retained 62, 42, and 43% of their initial (20 hr) peroxisomal beta-oxidation activity throughout 92 hr of culture. Ciprofibrate, bezafibrate, and LY171883 caused a dose-related increase in beta-oxidation in rat hepatocytes to a maximum of 10-, 8-, and 5-fold, respectively. In dog and monkey hepatocytes the increases in beta-oxidation were less than 2-fold. Peroxisome morphology in dog and monkey hepatocytes appeared to be unchanged by the drugs. Morphometric analysis in monkey hepatocytes showed no increase in peroxisome volume fraction in response to the chemicals. Treatment of dog and monkey hepatocytes with dexamethasone and glucagon during the final 24 hr in culture caused a 4- to 6-fold increase in tyrosine aminotransferase activity. This induction is characteristic of the in vivo response. The small increase in beta-oxidation reflects the relative insensitivity of the dog and monkey liver to peroxisome proliferators in vivo rather than a loss of sensitivity during culture. Cultured hepatocytes from beagle dog and rhesus monkey may provide a model for studying the mechanisms underlying the interspecies differences. Such information would help clarify the relevance of rodent data in human risk assessment.
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PMID:Effect of ciprofibrate, bezafibrate, and LY171883 on peroxisomal beta-oxidation in cultured rat, dog, and rhesus monkey hepatocytes. 197 28


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