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 effects of the alpha-adrenergic agonist phenylephrine on the levels of adenosine 3':5'-monophosphate (cAMP) and the activity of the cAMP-dependent protein kinase in isolated rat liver parenchymal cells were studied. Cyclic AMP was very slightly (5 to 13%) increased in cells incubated with phenylephrine at a concentration (10(-5) M) which was maximally effective on glycogenolysis and gluconeogenesis. However, the increase was significant only at 5 min. Cyclic AMP levels with 10(-5) M phenylephrine measured at this time were reduced by the beta-adrenergic antagonist propranolol, but were unaffected by the alpha-blocker phenoxybenzamine, indicating that the elevation was due to weak beta activity of the agonist. When doses of glucagon, epinephrine, and phenylephrine which produced the same stimulation of glycogenolysis or gluconeogenesis were added to the same batches of cells, there were marked rises in cAMP with glucagon, minimal increases with epinephrine, and little or no changes with phenylephrine, indicating that the two catecholamine stimulated these processes largely by mechanisms not involving cAMP accumulation. DEAE-cellulose chromatography of homogenates of liver cells revealed two major peaks of cAMP-dependent protein kinase activity. These eluted at similar salt concentrations as the type I and II isozymes from rat heart. Optimal conditions for preservation of hormone effects on the activity of the enzyme in the cells were determined. High concentrations of phenylephrine (10(-5) M and 10(-4) M) produced a small increase (10 tp 16%) in the activity ratio (-cAMP/+cAMP) of the enzyme. This was abolished by propranolol, but not by phenoxybenzamine, indicating that it was due to weak beta activity of the agonist. The increase in the activity ratio of the kinase with 10(-5) M phenylephrine was much smaller than that produced by a glycogenolytically equivalent dose of glucagon. The changes in protein kinase induced by phenylephrine and the blockers and by glucagon were thus consistent with those in cAMP. Theophylline and 1-methyl-3-isobutylxanthine, which inhibit cAMP phosphodiesterase, potentiated the effects of phenylephrine on glycogenolysis and gluconeogenesis. The potentiations were blocked by phenoxybenzamine, but not by propranolol. Methylisobutylxanthine increased the levels of cAMP and enhanced the activation of protein kinase in cells incubated with phenylephrine. These effects were diminished or abolished by propanolol, but were unaffected by phenoxybenzamine. It is concluded from these data that alpha-adrenergic activation of glycogenolysis and gluconeogenesis in isolated rat liver parenchymal cells occurs by mechanisms not involving an increase in total cellular cAMP or activation of the cAMP-dependent protein kinase. The results also show that phosphodiesterase inhibitors potentiate alpha-adrenergic actions in hepatocytes mainly by a mechanism(s) not involving a rise in cAMP.
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PMID:Studies on the alpha-andrenergic activation of hepatic glucose output. II. Investigation of the roles of adenosine 3':5'-monophosphate and adenosine 3':5'-monophosphate-dependent protein kinase in the actions of phenylephrine in isolated hepatocytes. 0 57

Tryptophanyl peptide bonds are selectively cleaved by N-chlorosuccinimide (NCS) under acidic conditions. All other peptide bonds are resistant to cleabage by this reagent. Optimal conditions for cleavage are: 2 equiv of NCS, pH 4-5, or 50-80% acetic acid for 30 min at room temperature. Under these conditions methionine residues are oxidized to methionine sulfoxides and cysteine. Other amino acids are not modified. The cleavage reaction was studied with several peptides containing tryptophan residueas successfully applied to several proteins. In alpha-lactalbumin, Kunitz trypsin inhibitor ,and apomyoglobin, selective cleavage of the expected tryptophanyl peptide bonds was obtained in 19-58% yield. The glucagon molecule was fragmented into two peptides in 32% yield.
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PMID:Selective chemical cleavage of tryptophanyl peptide bonds by oxidative chlorination with N-chlorosuccinimide. 99 Feb 66

The glucagonoma syndrome is characterized by a necrolytic migratory erythematous rash, angular stomatitis, painful glossitis, a normochromic normocytic anemia, mild diabetes mellitus, weight loss, a tendency to thrombosis, and neuropsychiatric disturbances. The diagnosis is made by finding a high plasma glucagon concentration in the absence of any other cause, such as renal failure or severe stress. A pancreatic alpha-cell tumor can be identified and stained by immunocytochemistry with glucagon antibodies. Optimal treatment is surgical removal, but approximately 50 percent of the tumors have metastasized by the time of diagnosis. Since the tumor is slow-growing, remission can be obtained by hepatic artery embolization to shrink hepatic secondaries or by shrinkage, in about 10 percent of patients, with the combination chemotherapeutic regimen of 5-fluorouracil and streptozotocin. The rash frequently responds to administration of zinc, a high-protein diet, and control of the diabetes with insulin. Alongside the alpha cell in the islets of Langerhans is the D-cell, which produces somatostatin and may well act physiologically as a paracrine inhibitor of glucagon release. A newly developed, long-acting somatostatin analogue, SMS 201-995, which the patient can self-administer as a subcutaneous injection, has proven effective in suppressing glucagon secretion from glucagonomas and, in some cases, causing remission of clinical symptoms.
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PMID:Glucagonoma syndrome. 288 77

The purpose of the present investigation was to characterize and determine what hormones affect the activity of aromatase in human fetal hepatocytes maintained in primary monolayer culture. The major product of aromatization of androstenedione was estrone sulfate. Optimal conditions for assay of aromatase activity in fetal liver cells were determined. The apparent Km for androstenedione was 50 nM. Aromatase activity was stimulated by glucocorticoids in the presence of fetal calf serum. The concentration of dexamethasone required for half-maximal stimulation was 10(-8) M, similar to the concentration required for half-maximal binding to glucocorticoid receptors. This action of dexamethasone was inhibited by cortisol 21-mesylate, a glucocorticoid antagonist. Aromatase activity was also stimulated by (Bu)2cAMP and cholera toxin, and was inhibited by fetal calf serum. This effect of fetal calf serum was mimicked by epidermal growth factor. However, epidermal growth factor did not mimic the permissive action of serum to stimulate aromatase activity by dexamethasone. In these respects, the regulation of aromatase activity of human fetal hepatocytes is similar to that of human adipose stromal cells. A polycyclic hydrocarbon, benzo(a)pyrene, which causes induction of aryl hydrocarbon hydroxylase activity in fetal hepatocytes, inhibited the stimulation of aromatase activity by dexamethasone. Of a number of hormones tested, including glucagon, insulin, angiotensin II, ACTH, hCG, GH, PRL, and T3, only glucocorticoids were effective in stimulating aromatase activity of human fetal hepatocytes. These results emphasize the complex and multiparameter nature of the regulation of aromatase activity in this as in other tissues.
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PMID:Factors affecting the conversion of androstenedione to estrogens by human fetal hepatocytes in monolayer culture. 298 22

Optimal and early control of recent onset, type I diabetes by intensive insulin therapy has been reported to allow insulin withdrawal in about two thirds of subjects treated. We used continuous s.c. insulin infusion (CSII) in the attempt to induce a temporary remission of insulin dependence in 18 newly diagnosed young adult diabetics. After 10 days of optimized glycometabolic control, insulin infusion was stopped and patients were switched to glibenclamide (15 mg/die) plus metformin (1 g/die). Diabetics were considered in remission of insulin dependence when their metabolic control fulfilled the following criteria for at least 3 months: absence of glycosuria, pre- and post-prandial blood glucose less than or equal to 120 and 180 mg/dl, respectively, HbA1c less than or equal to 7%. Insulin therapy could be discontinued for periods of over three months in 11 subjects (61%) and for as long as 18 months in one case. Insulin requirement during CSII was slightly higher in nonremitters (NR) than in remitters (R): 0.36-0.64 vs 0.26-0.41 U/kg/die. After 24 months from CSII, R still showed lower insulin requirement (0.35-0.42 U/kg/die) than NR (0.55-0.75 U/kg/die). Further, the role of some hormonal and immunologic factors was investigated. Plasma C-peptide and glucagon were measured, fasting and 2h after each meal, both on admission and immediately after CSII, when patients were switched to oral therapy. No difference in hormone levels could be detected on admission, whereas, after CSII, mean post-prandial increase of C-peptide over basal was significantly higher in R than in NR (1.18 +/- 0.37 vs 0.22 +/- 0.16 ng/ml, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Remission from insulin dependence induced by continuous subcutaneous insulin infusion (CSII) in type I, newly diagnosed diabetics: role of some hormonal and immunologic factors. 326 1

Specific binding sites for secretin have been identified in rat fundic membranes, using 125I-secretin. The binding was saturable, reversible, time and temperature dependent. Optimal pH for binding was around 7-7.5. Scatchard plots were compatible with the existence of 2 classes of receptors; the first class with a high affinity for secretin (apparent Kd of 4 x 10(-10) M) and a low binding capacity (150 fmol per mg membrane protein, i.e., 4,500 high affinity sites/cell) and a class of receptors with a lower affinity (Kd of 3 x 10(-9) M) and a higher binding capacity (580 fmol per mg membrane protein i.e., 17,400 sites/cell). Glucagon, gastric inhibitory polypeptide and somatostatin had no-effect on secretin binding. In contrast, VIP inhibited 125I-secretin binding and stimulated adenylate cyclase activity, in both cases at a 200-times lower potency than secretin (ID50 and Ka = 2 x 10(-7) M VIP). The properties of these secretin receptors strongly support the concept that secretin acts as a regulatory peptide on the rat gastric epithelium.
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PMID:Secretin binding sites coupled with adenylate cyclase in rat fundic membranes. 628 94

Metabolic fluxes (Ra and Rd) are calculated in the nonsteady state using Steele's equations. These calculations require estimates of the values and rates of change of glucose and specific activity at discrete sampling times. Data smoothing minimizes the effect of measurement error that confounds the Ra and Rd calculations. We compared three smoothing methods: a) moving average, b) polynomial fitting, and c) optimal segments, a new technique that utilizes optimization methods. Experimental designs were simulated: 1) constant infusion of glucagon in depancreatized dogs, and 2) glucose oscillations generated by constant high-level glucose infusion. Measurement error was added to raw data. After smoothing, fluxes were calculated and compared to the "actual" Ra and Rd. Ra calculated from unsmoothed noisy data were in error by an average 39%. Error was reduced by smoothing to: 23%, moving average; 18%, polynomial fitting; 15%, optimal segments. Optimal segments was best for calculating Ra (P less than 0.01) and was better than or equal to other methods for Rd. Distortion in flux patterns was greatest for polynomial fitting (P less than 0.01) and least for optimal segments (P less than 0.001). Optimal segments is the method of choice for smoothing tracer data; it improves calculations of Ra and Rd with minimal distortion.
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PMID:Optimal segments: a method for smoothing tracer data to calculate metabolic fluxes. 684 33

Adenylate cyclase [ATP pyrophosphate lyase (cyclizing), EC 4.6.1.1] was shown to be present in cultured human articular chondrocytes. Optimal conditions of incubation time, protein and substrate concentrations and pH were determined in whole cell lysates. Maximal activity occurred at pH 8.5 with no decrease in activity up to pH 10.0. Adenylate cyclase activity of particulate membrane preparations was enhanced by the addition of crude cytosol preparations. The prostaglandins E1, E2, F1 alpha, F2 alpha, D2, B1, B2, A1 and A2, as well as adrenaline and isoprenaline, stimulated adenylate cyclase derived from either adult or foetal chondrocytes. No significant stimulation was observed in the presence of human calcitonin or glucagon. Bovine parathyroid hormone always significantly stimulated the adenylate cyclase derived from foetal chondrocytes, but not from adult chondrocytes. Preincubation of the chondrocytes in culture with indomethacin and with or without supernatant medium from cultured mononuclear cells increased the responsiveness of the adenylate cyclase to prostaglandin E1.
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PMID:Adenylate cyclase of human articular chondrocytes. Responsiveness to prostaglandins and other hormones. 715 97

Essential fatty acids (EFA), which are not synthesized in animal and human tissues, belong to the n-6 and n-3 families of polyunsaturated fatty acids (PUFA), derived from linoleic acid (LA, 18:2n-6) and alpha-linolenic acid (LNA, 18:3n-3). Optimal requirements are 3-6% of ingested energy for LA and 0.5-1% for LNA in adults. Requirements in LNA are higher in development. Dietary sources of LA and LNA are principally plants, while arachidonic acid (AA, 20:4n-6) is found in products from terrestrian animals, and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are found in products from marine animals. EFA are principally present in dietary triacylglycerols, which should be hydrolyzed by lipases in gastric and intestinal lumen. DHA seems to be released more slowly than the others. Its intestinal absorption is delayed but not decreased. Long-chain PUFAs are incorporated in noticeable amounts in chylomicron phospholipids. However, their uptake by tissues is no more rapid than uptake of shorter chain PUFA. In tissues, LA and LNA, which constitute the major part of dietary EFA, should be converted into fatty acids of longer and more unsaturated chain by alternate desaturation (delta 6, delta 5, delta 4)-elongation reactions. Animal tissues are more active in this biosynthesis than human tissues. Liver is one of the most active organs and its role is critical in providing less active tissues, particularly the brain, with long-chain PUFA secreted in VLDL (very low density lipoprotein). In liver, many nutritional, hormonal and physiological factors act on the PUFA biosynthesis. Dietary fatty acids exert a great influence and are often inhibitory. Dietary LNA inhibits delta 6 desaturation of LA. The desaturation products AA, EPA, and DHA inhibit delta 6 desaturation of LA and delta 5 desaturation of DGLA (dihomo-gamma-linolenic acid). With regard to hormones, insulin and thyroxin are necessary to delta 6 and delta 5 desaturation activities, whereas other hormones (glucagon, epinephrine, ACTH, glucocorticoids) inhibit desaturation. Concerning the physiological factors, the age of individuals is critical. In the fetus, the liver and the brain are capable of converting LA and LNA into longer-chain EFA, but these are also delivered by the mother, after synthesis in the maternal liver and placenta. Just after birth, in animals, the delta 6 desaturation activity increases in the liver and decreases in the brain. In aging, the capacity of the whole liver to desaturate LA and DGLA is equal at 1.5 and 25 months of age in rats fed a balanced diet throughout their life and the AA and DHA content of tissue phospholipids is unchanged in aging.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The metabolism and availability of essential fatty acids in animal and human tissues. 784 Aug 71

Optimal blood glucose levels and normal insulin sensitivity are aims in the treatment of insulin-dependent diabetes mellitus (IDDM). Insulin sensitivity and insulin reserve are closely interrelated. It is essential to know more about both of these parameters at clinical diagnosis, because their preservation may delay the occurrence of diabetes-related complications. B-cell function is likely to be retained for a longer period in patients with adult onset of the disease compared with children. In this study, intensive insulin treatment was initiated in newly diagnosed adult patients to determine if it preserved endogenous insulin secretion longer than conventional therapy. Forty-nine patients with newly diagnosed diabetes were carefully categorized as having IDDM according to clinical and serological criteria. They were randomized to an intensive (I group) or conventional (C group) insulin therapy and evaluated for 5 years. Every 6 months, a check-up included glucagon-stimulated C-peptide (GSCP), hyperglycemic glucose clamp with arginine bolus, euglycemic-hyperinsulinemic clamp, and screening for microalbuminuria, retinopathy, and neuropathy. At the end of the study, hemoglobin A1c (HbA1c) was 6.3% +/- 1.9% in the I patients and 8.1% +/- 2.1% in the C patients (P < .001). Blood glucose concentrations less than 3.5 mmol/L were more frequent in the I group than in the C group (P < .05). Insulin sensitivity (M/I) and GSCP were higher in intensively treated patients after 5 years (M/I, I group 40 +/- 10 nmol x kg(-1) x min(-1) x pmol/L1 v C group 21 +/- 11, P < .005; GSCP, I group 0.6 +/- 0.2 nmol/L v C group 0.19 +/- 0.11, P < .005). The prevalence of peripheral neuropathy was significantly lower in the I group at the end of the study. In conclusion, intensive therapy is more effective in the preservation of insulin action and reserve. In our patients, no case of severe hypoglycemia was observed, indicating that intensive therapy was safe in these patients.
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PMID:Intensive therapy in adult insulin-dependent diabetes mellitus is associated with improved insulin sensitivity and reserve: a randomized, controlled, prospective study over 5 years in newly diagnosed patients. 896 84


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