Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.4.1 (phosphodiesterase)
18,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Partially purified, non-suppressible, insulin-like material (NSILA-S) was studied with respect to its effect on the levels of 3',5'-cyclic adenosine monophosphate (cAMP) and its mechanism of action in the control of this nucleotide in rat fat cells. NSILA-S prevents the rise of cAMP in fat cells under the influence of isoproterenol with similar kinetics to insulin. A maximal effect is observed at about 70 ng/ml with a biological activity equivalent to 200 muU/ml of insulin. NSILA-S inhibits norepinephrine-stimulated adenylate cyclase activity in fat cell ghosts and partially purified plasma membrane preparations. At 10 mM Mg2+, the inhibition is characterized by an effect of Vmax without change in affinity towards ATP (apparent KM 30 muM). Similarly there is no observed change in affinity towards Mg2+. With respect to inhibition of norepinephrine-stimulated adenylate cyclase, the dose-response curve of NSILA-S is similar to that already found with intact cells. The effect of norepinephrine is inhibited throughout the dose-response range between 5 X 10(-7) and 5 X 10(-4) M. In contrast to previous observations with insulin in ghosts, NSILA-S inhibits the basal adenylate cyclase activity. Cyclic nucleotide phosphodiesterase activity in homogenates as measured at 1.0 muM substrate is increased by 90% after previous incubation of fat cells with NSILA-S. The study suggests that the anti-lipolytic effect of NSILA-S is mediated by a lowering of cAMP through inhibition of the adenylate cyclase and/or stimulation of the phosphodiesterase system.
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PMID:Effect of partially purified NSILA on adenylate cyclase, phosphodiesterase and 3',5'-cyclic AMP in fat cells. 17 93

Insulin-induced hypoglycemia previously has been shown to provoke a beta-adrenergic response that normally results in an increase in plasma renin activity (PRA). In our study, hypoglycemia induced definite increases in PRA in a group of five patients with normal renin essential hypertension but failed to do so in a group of six patients with low renin essential hypertension. In both groups, plasma cyclic adenosine 3',5'-monophosphate (cyclic AMP; cAMP) increased more than 2-fold during hypoglycemia, but the response in the low renin group was significantly less than that previously observed in normal subjects under the same conditions. Plasma cortisol increased to an equal extent in both groups of hypertensive patients during hypoglycemia. Infusion of the phosphodiesterase inhibitor, theophylline, resulted in definite increases of PRA in patients with normal renin hypertension but not in patients with low renin hypertension. Because changes in the level of plasma cAMP during hypoglycemia have been thought to reflect adrenal catecholamine release, our finding of a blunted increase in plasma cAMP during hypoglycemia in patients with low renin hypertension may suggest that there is a generalized alteration in adrenergic responsiveness in this condition.
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PMID:Contrasting effects of hypoglycemia on plasma renin activity and cyclic adenosine 3',5'-monophosphate (cyclic AMP) in low renin and normal renin essential hypertension. 17 76

Cadmium, in addition to producing a variety of toxic manifestations, is known to accumulate in certain "target" organs which include liver and kidney where histological and functional damage becomes apparent. The daily intraperitoneal injection of cadmium chloride for 21 or 45 days stimulated the activities of hepatic pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose-1, 6-diphosphatase and glucose-6-phosphatase elevated blood glucose and urea, and lowered hepatic glycogen in rats. Whereas chronic Cd treatment failed to alter adenosine-3', 5'-monophosphate phosphodiesterase (PDE) activity, cyclic AMP (cAMY and the activity of basal and fluoride-stimulated forms of hepatic adenylate cyclase (AC) were markedly increased. However, the cAMP binding to hepatic protein kinase was decreased as was the kinase activity ration. An acute dose of Cd decreased hepatic glycogen content and increased blood glucose, serum urea, and hepatic cAMP. Chronic exposure to Cd induced adrenal hypertrophy and augmented adrenal norepinephrine and epinephrine as well as the activity of adrenal tyrosine hydroxylase. This treatment decreased prostatic and testicular weights of mature rats. Although cAMP as well as AC activity of the prostate gland were reduced, cAMP binding to the prostatic protein kinase was increased as was the activity of the cAMP-dependent form of the enzyme. Testicular AC and PDE activities, however, were stimulated, although cAMP remained unaffected. Whereas the activities of the cAMP-dependent and the independent forms of testicular protein kinase were significantly depressed, the binding of cAMP to protein kinase from testes of Cd-treated rats was not affected. In most cases, the observed metabolic alterations persisted up to 28 days on cessation of Cd administration. Subacute Cd treatment suppressed pancreatic function as evidenced by lowered serum immunoreactive insulin (IRI) in presence of hyperglycemia, as well as by partial inhibition of phentolamine-stimulated increases in serum IRI. Although chronic Cd treatment failed to alter the concentration of brain stem norepinephrine and cerebrocortical acetylcholine esterase activity, serotonin levels of brain stem were depressed and the concentration of striatal dopamine and cerebrocortical acetylcholine were significantly elevated when compared with the values seen in control nonexposed animals.
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PMID:Aspects of the biochemical toxicology of cadmium. 17 84

The purpose of the present study was to investigate the regulation of insulin biosynthesis during the perinatal period. The incorporation of [3H]leucine into total immunoreactive insulin (IRI) and into IRI fractions was measured by a specific immunoprecipitation procedure after incubation, extraction, and gel filtration in isolated 3-day-old rat pancreases without prior isolation of islets. IRI fractions were identified by their elution profile, their immunological properties, and their ability to compete with the binding of 125 I-insulin in rat liver plasma membranes. No specific incorporation of [3H]leucine was found in the IRI eluted in the void volume, making it unlikely that this fraction behaves as a precursor of (pro) insulin in this system. In all conditions tested, the incorporation of [3H]leucine was linearly correlated with time. Optimal concentration of glucose (11 mM) activated six- to sevenfold the [3H]leucine incorporation into IRI. Theophylline or N6O2-dibutyryl- (db) cAMP at 1.6 mM glucose significantly increased the [3H]leucine incorporation. Glucose at 16.7 mM further enhanced the effect of both drugs. Contrarily, somatostatin (1-10 mug/ml) inhibits the rate of [3H]leucine incorporation into IRI in the presence of 11 mM glucose; this effect was observed at 5.5 mM glucose and was not modified by any further increase in glucose concentrations up to 27.5 mM. Theophylline or dbcAMP at 10 mM concentration did not reverse the somatostatin inhibitory effect on either insulin biosynthesis or release. Somatostatin also inhibited both processes in isolated islets from the 3-day-old rat pancreas. High Ca++ concentration in the incubation medium reversed the inhibitory effect of somatostatin on glucose-induced insulin biosynthesis as well as release. In both systems the inhibitory effect of somatostatin on insulin biosynthesis and release correlated well. Glipizide (10-100 muM) AND TOLBUTAMIDE (400 MUM) inhibited the stimulatory effect of glucose, dbcAMP, and theophylline on [3H]leucine incorporation into IRI. The concentrations of glipizide that were effective in inhibiting [3H]leucine incorporation into IRI were smaller than those required to inhibit the phosphodiesterase activity in isolated islets of 3-day-old rat pancreas. These data suggest the following conclusions: (a) the role of the cAMP-phosphodiesterase system on insulin biosynthesis is likely to be greater in newborns than in adults; (b) the greater effectiveness of glucose and the cAMP system on insulin biosynthesis than on insulin release might possibly be related to the rapid accumulation of pancreatic IRI which is observed in the perinatal period; (c) somatostatin, by direct interaction with the endocrine tissue, can inhibit glucose and cAMP-induced insulin biosynthesis as well as release; calcium reverses this inhibition; (d) sulfonylureas inhibit insulin biosynthesis in newborn rat pancreas an effect which has to be considered in the use of these agents in human disease.
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PMID:Biosynthesis of proinsulin and insulin in newborn rat pancreas. Interaction of glucose, cyclic AMP, somatostatin, and sulfonylureas on the (3H) leucine incorporation into immunoreactive insulin. 17 41

The activity of ornithine decarboxylase increases markedly in a biphasic manner during the hormone-dependent development of mouse mammary epithelium in vitro. The first peak of activity occurring at 3 to 4 hours of culture was elicited by incubating mammary explants in a culture medium without any added hormones, although addition of insulin or prolactin, or both, caused a greater increase. The emergence of the second peak of activity at about 12 hours depended on the actions of both insulin and prolactin. A second increase in activity could also be effected postmitotically by the delayed addition of prolactin. Studies with actinomycin D and cycloheximide suggest that the first increase in enzyme activity may be effected at a post-transcriptional level, whereas a second increase may be at both transcriptional and translational levels. During the first 3 hours of incubation, there was a rapid, transient increase in cyclic AMP concentration in mammary epithelium. The presence of insulin or prolactin in culture did not affect the change in epithelial cyclic AMP concentration. Addition of several derivatives of cyclic AMP, 0.1 to 0.5 mM, as well as prostaglandin E1, a stimulator of adenylate cyclase, resulted in enhancement of the first increase in enzyme activity. The effect of cyclic nucleotide was additive to that of insulin and prolactin and appears to be mediated at a post-transcriptional level. The stimulatory effect of a lower concentration of both the cyclic nucleotide and prostaglandin E1 was augmented by theophylline, an inhibitor of phosphodiesterase. These results may suggest possible involvement of cyclic AMP in the first increase in enzyme activity that occurs in the absence of any added hormones.
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PMID:Studies on regulatory factors of ornithine decarboxylase activity during development of mouse mammary epithelium in vitro. 17 59

In adult albino rats, increased sentivity of the organism to insulin action caused by systematic muscular exercises preserved in conditions of adrenergic blockade but was reduced by theophylline administration (inhibition of 3'-5'-AMP-phosphodiesterase activity). The sensitivity to insulin action 3'-5'-phosphodiesterase (in muscles, liver, and adipose tissue) increased during adaptation to muscular activity. Simultaneously the insulin inactivation in muscle and liver tissues also increased.
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PMID:[Analysis of an increase in the body's sensitivity to insulin]. 17 1

In trained adult albino rats, more rapid mobilization of carbohydrates and FFA, more economical carbohydrates expenditure during muscular exercise, and more rapid resynthesis of glycogen during recovery period, were observed. This depends on both the changes of 3',5'-AMP-phosphodiesterase activity of muscles, liver, and adipose tissue, and the degree of insulin inactivation by muscle and liver tissues. Both these processes considerably differ in untrained and trained animals.
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PMID:[The activity of 3',5'-AMP phosphodiesterase and inactivation of insulin during muscular activity]. 17 2

Insulin accelerates the entry of glucose and amino acids into muscle cells by acting upon the 'carrier-facilitated' transport mechanism. For glucose this process is passive and leads to equilibration of intracellular and extracellular concentrations. In heart muscle, glucose transport is a rate-limiting step for glucose uptake. During hypoxia and ischemia the heart turns to anaerobic glycolysis for energy production and therefore, maximal glucose transport becomes important. Insulin is necessary to insure proper protein synthesis, probably at the level of membrane-bound polyribosomes. However, during myocardial hypoxia, insulin alone cannot restore the associated depression in protein synthesis. Although insulin hyperpolarizes the cell, a change in the ratio of intracellular to extracellular activities of potassium is not its primary mode of action. An insulin-induced configurational change in the plasma membrane could simultaneously account for the effects of insulin on sodium and potassium permeability and the action on facilitated transport. Intracellular levels of cyclic adenylate may be reduced by insulin in adipose tissue because of inhibition of adenyl cyclase or stimulation of phosphodiesterase. However, at this time there is little evidence that insulin alters cyclic AMP levels in the heart. Insulin secretion is depressed in patients with heart disease in proportion to the reduction of cardiac index sustained. Since the ischemic heart is dependent upon glucose as the major fuel, insulin lack may deprive the heart of adequate substrate.
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PMID:Insulin: fundamental mechanism of action and the heart. 18 67

The in vitro effects of insulin on different phosphodiesterase activities present in rat epididymal fat cells from normal and hypothyroid rats have been studied. Evidence is presented that insulin increases the maximum velocity of a particulate, low Km, cyclic adenosine-3', 5'-monophosphate (cyclic AMP) phosphodiesterase in both types of cells, this effect being more clearly evident with the fat cells from hypothyroid animals; combination of insulin and thyroidectomy resulted in a 400% stimulation with 10-10 - 10-9 M insulin. A clear and significant effect was apparent at 10-11 M insulin. However, the dose-response curve was biphasic, since stimulation by insulin was suppressed for doses of hormone higher 10-8 - 10-7 M. Moreover, insulin effects were very fast, since clear stimulation was observed after only 2 min of incubation; the maximal increase was obtained after 10 min. Insulin did not significantly affect the soluble cyclic AMP phosphodiesterase activity in normal cells, thus confirming results obtained by others. However, the soluble cyclic AMP phosphodiesterase activity was clearly stimulated by insulin when the fat cells were prepared from hypothyroid rats. Maximal stimulation was obtained with 10-9 M insulin; the response was again very fast. Soluble cyclic GMP phosphodiesterase activity was also increased additively by hypothyroidism and insulin, maximal stimulation being obtained with 10-9 M insulin. With this dose of insulin the additive effects of thyroidectomy and insulin produced a 5-fold stimulation. The effect of insulin on the soluble cyclic GMP phosphodiesterase was very fast (2-5 min). With both soluble cyclic nucleotide phosphodiesterase activities, insulin increased the maximal velocity but not apparent Km of the enzyme. Thus, hypothyroidism and insulin produced additive effects suggesting a different mechanism of action of these two hormonal situations on the degradation of the intracellular pools of cyclic AMP and cyclic GMP.
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PMID:Cyclic nucleotide phosphodiesterases, insulin and thyroid hormones. 18 75

Control of the levels of cAMP in the early phase after addition of catecholamines and the effect of insulin is discussed under consideration of own findings from experiments with isolated fat cells of the rat. Data on the kinetics of cAMP are interpreted in the light of results from several groups of a rapid activation of phosphodiesterase activity along with the adenylate cyclase system. Comparison of energy metabolism of fat cells with the formation of cAMP under conditions of near-maximal activation of the adenylate cyclase system by isoproterenol shows that about half of the cellular ATP turnover is used for information transfer. Insulin reduces cAMP concentrations in the presence of isoproterenol within one min of incubation when added either together with or after the catecholamine. Experiments with propranolol and the phosphodiesterase inhibitor, methyl isobutylxanthine suggest an effect of insulin on formation and breakdown of cAMP.
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PMID:Hormonal control of cyclic AMP turnover in isolated fat cells. 18 81


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