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:3.5.4.4 (adenosine deaminase)
5,136 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

ACTH at levels as low as 0.05 mU/ml stimulated lipolysis, protein kinase and cyclic AMP accumulation in isolated fat cells from fed and fasted rats. Changes in cyclic AMP levels and in the protein kinase activity ratio were well correlated temporally. The protein kinase activity ratio was potentiated by adenosine deaminase. A sudden increase or decrease in either ACTH or dibutyryl cyclic AMP concentration was associated with a rapid and corresponding change in the rate of glycerol production. With ACTH, the changes in glycerol production were accompanied by appropriate changes in cyclic AMP levels. Actinomycin-D (10 UM) did not affect lipolysis or cyclic AMP accumulation activated by ACTH in fat cells.
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PMID:The correlation of cyclic AMP and protein kinase activity in adipocytes with lipolysis stimulated by ACTH: the effect of adenosine deaminase and actinomycin D. 21 72

The effects of cold exposure (7 days, 5 degrees C) and cold acclimation (21 days, 5 degrees C) on the regulation of lipolysis were investigated in adipocytes isolated from epididymal fat pads of rats. Catecholamines stimulated lipolysis in an affinity sequence typical of the beta 1-adrenoceptor subtype: one-half maximum velocity (1/2 Vmax) isoproterenol (35 nM) much greater than 1/2 Vmax norepinephrine (150 nM) approximately 1/2 Vmax epinephrine (200 nM). Cold exposure markedly decreased the sensitivity (1/2 Vmax) and the responsiveness (Vmax) of the adipocytes to the lipolytic action of catecholamines. Addition of adenosine deaminase to fat cells isolated from cold-exposed rats did not normalize the lipolytic activity, suggesting that extracellular adenosine was not responsible for the obtunded lipolysis. This effect of cold exposure was transient as the lipolytic response to catecholamines was normal in fully cold-acclimated animals. Remarkably, the responsiveness of adipocytes to the lipolytic action of glucagon (200 nM) and adrenocorticotropic hormone (ACTH, 1 microM) progressively increased during cold acclimation. Adipocyte lipolytic response to dibutyryl adenosine 3',5'-cyclic monophosphate (cAMP) and theophylline was normal in cold-exposed rats, indicating that the lipolytic defect resides at an early step in the lipolytic cascade (pre-cAMP). On the other hand, the antilipolytic effect of insulin on norepinephrine-induced lipolysis significantly decreased during cold acclimation, particularly at physiological levels of insulin (nanomolar level). These results demonstrate that the transient decrease in the lipolytic action of catecholamines observed during cold acclimation is compensated by 1) an increased responsiveness of adipocytes to glucagon and ACTH and 2) by a decreased effectiveness of insulin to induce antilipolysis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Alterations in adipocyte response to lipolytic hormones during cold acclimation. 215 29

The inhibition of insulin-stimulated glucose transport by lipolytic agents was studied in isolated rat adipose cells. Two different mechanisms for the inhibition of glucose transport by lipolytic hormones and agents were distinguished by use of the antilipolytic agent prostaglandin E2 (PGE2). The inhibition of glucose transport induced by lipolytic hormones such as glucagon, catecholamines or ACTH in the presence of adenosine deaminase was antagonized by PGE2. In contrast, inhibition of hexose transport by alkylxanthines was only partially (20-30%) attenuated by PGE2, although the eicosanoid had antagonized cyclic AMP accumulation and stimulation of lipolysis in response to all tested lipolytic agents. The inhibition of glucose transport by IBMX was immediate, whereas the lipolytic hormones (isoprenaline and ACTH) exhibited a latency of 2-3 min. In addition, the inhibition induced by the lypolytic hormones disappeared after cooling of the cells to 22 degrees C, at which temperature IBMX was still inhibitory. Thus, the PGE2-sensitive component of the effect of lipolytic agents on glucose transport appears to be mediated by adenylate cyclase or its subunits Ns/Ni. The PGE2-insensitive effect of alkylxanthines probably reflects a direct interaction of the agents with a regulatory site at the transporter or a related protein.
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PMID:Prostaglandin E2 differentiates between two forms of glucose transport inhibition by lipolytic agents. 244 31

Crude preparations of histones had insulin-like actions in isolated adipocytes. This activity was attributed to the arginine-rich histones, H3 and H4. The metabolic effects of purified H3 and H4 on isolated adipocytes were similar to those of insulin in a number of respects. Like insulin, H3 and H4 stimulated the incorporation of both glucose and pyruvate in isolated cells and stimulated intercellular oxidation of glucose; in contrast, the lipolytic agents ACTH and isoproterenol actually inhibited the incorporation of pyruvate into adipocytes. In contrast to the effects of the lipolytic hormones, the effects of H3 and H4, like insulin, were not blocked by the presence of adenosine deaminase in the medium. The same concentrations of phenylarsine oxide were required to inhibit the stimulation of glucose incorporation whether by insulin or by histones. Furthermore, the addition of H4 or insulin to isolated adipocytes resulted in the increased phosphorylation of 17 kDa phosphoproteins as detected by two-dimensional electrophoresis. The insulin-like effect of the active histones was specific to their structure. Lysine-rich histones (H1, H2A and H2B), various polycations, and proteolytic fragments of purified H3 or H4 were all inactive. It is unknown whether this phenomenon might imply a physiological function for such endogenous molecules; however, a comparison of the detailed effects of insulin and histones might be informative in terms of common intracellular transduction systems.
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PMID:Insulin-like effects of histones H3 and H4 on isolated rat adipocytes. 254 Aug 34

We have recently shown the presence of adenosine receptors coupled to adenylate cyclase in anterior pituitary and in the present studies we have investigated the effects of adenosine on ACTH release. The 'R'-site specific analogs of adenosine such as N-Ethylcarboxamide adenosine (NECA), L-N6-phenylisopropyl adenosine (PIA), 2-chloro-adenosine (2-Cl-Ado) all stimulated ACTH release in a dose-dependent manner. NECA was the most potent analog and stimulated ACTH release by about 170% with an apparent Ka of 0.1 microM, whereas PIA and 2-Cl-Ado were less potent and stimulated the release by about 110% and 125% with an apparent Ka of 0.2 and 0.4 microM respectively. The stimulation of ACTH release by NECA was inhibited by 3-isobutyl-1-methylxanthine (IBMX). On the other hand, adenosine deaminase (ADA) treatment of the cells also stimulated ACTH release as well as adenylate cyclase activity by about 2-fold, suggesting that endogenous adenosine plays an inhibitory role in the release of ACTH. Other agents, such as corticotropin-releasing factor (CRF), vasoactive intestinal peptide (VIP) and forskolin (FSK) also stimulated ACTH release from these cells. In addition, the stimulation by an optimal concentration of NECA was almost additive with maximal stimulation caused by VIP and FSK. These data suggest that adenosine modulates ACTH release from anterior pituitary through its interaction with adenosine receptors coupled to adenylate cyclase.
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PMID:Adenosine regulates the release of adrenocorticotropic hormone (ACTH) from cultured anterior pituitary cells. 255 Jul 86

ACTH, isoprenaline, forskolin, and dibutyryl cyclic AMP prevented insulin from stimulating adipocyte pyruvate dehydrogenase in the presence of adenosine deaminase. Antagonism was reversed by N6-phenylisopropyladenosine as well as oxytocin. The stimulatory effects of insulin, adenosine and oxytocin on adipocyte pyruvate dehydrogenase appear to be through (a) mechanism(s) which is (are) similar or related.
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PMID:Adenosine and oxytocin reverse antagonism of cyclic AMP elevating agents to insulin activation of adipocyte pyruvate dehydrogenase. 303 Aug 21

The present communication shows the effects of several alpha-adrenergic agonists and antagonists on cyclic AMP levels in hamster epididymal adipocytes. In response to ACTH (30 mU/ml) in combination with 1-methyl-3-isobutylxanthine (0.10 mM) or adenosine deaminase (1.0 micrograms/ml), cyclic AMP levels increased to a maximum by 10 min and this level was maintained for another 20 min. Elevated cyclic AMP levels were partially suppressed by the alpha-adrenergic agents clonidine, methoxamine, methyl norepinephrine and phenylephrine. The lowest effective concentration of each of these agonists required to suppress cyclic AMP levels was 10 nM clonidine; 3 microM methoxamine; 10 microM methyl norepinephrine; 10 microM phenylephrine. Clonidine and methoxamine suppressed cyclic AMP levels by nearly 65% while phenylephrine and methyl norepinephrine caused only a 30% decline. Studies of the relative potencies of alpha-adrenergic blocking drugs on prevention of the inhibitor effect of clonidine on cyclic AMP levels disclosed that phentolamine and yohimbine were more potent blockers of clonidine action than phenoxybenzamine and prazosin. The rank order of potencies of agonists at causing suppression of cyclic AMP levels and the rank order of potencies of antagonists of clonidine action suggest similarity of the alpha-adrenergic receptors present on hamster adipocytes, which affect cyclic AMP accumulation to alpha-2 adrenergic receptors.
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PMID:Alpha-adrenergic inhibition of cyclic AMP accumulation in hamster adipocytes. Similarity of receptor with alpha-2 adrenergic receptors. 615 28

This communication shows the relative potencies of the alpha-agonists clonidine, methoxamine, methyl norepinephrine and phenylephrine in producing inhibition of lipolysis. At cell densities greater than 15 mg cell/ml lipolysis activated by either 1-methyl-3-isobutyl xanthine or adenosine deaminase was inhibited by alpha-adrenergic stimuli with a rank order of potency of clonidine greater than methoxamine greater than methyl norepinephrine; phenylephrine produced a further stimulation of lipolysis. At the same cell density isoproterenol-accelerated lipolysis was inhibited by alpha-adrenergic stimuli with a rank order of potency of phenylephrine greater than methoxamine greater than clonidine greater than methyl norepinephrine. When the density of fat cells was reduced to less than 5 mg/ml, clonidine was a more effective inhibitor of isoproterenol-activated lipolysis thatn phenylephrine. Lipolysis that was activated by dibutyryl cyclic AMP, ACTH or cholera enterotoxin was not reduced by any alpha-adrenergic agent. Under conditions when clonidine failed to inhibit catecholamine-activated lipolysis (i.e., at cell densities greater than 15 mg/ml), it failed to antagonize the antilipolytic activity of phenylephrine. The antilipolytic activities of clonidine and phenylephrine were most effectively antagonized by the blocking drugs phentolamine and yohimbine; in contrast, phenoxybenzamine and prazosin were less effective blockers. These data indicate that the alpha-adrenergic receptor on hamster fat cells is similar to presynaptic alpha-adrenergic receptors. The data further suggest the possibility that phenylephrine may exert its action through a separate alpha-adrenergic receptor mechanism.
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PMID:Inhibition of lipolysis in hamster adipocytes with selective alpha-adrenergic stimuli. Functional characterization of the alpha-receptor. 624 26

The isolated intact white adipocyte of the Swiss mouse responds to both ACTH and catecholamines by an elevation of cAMP levels and an increase in lipolysis. However, in the isolated plasma membrane of the mouse adipocyte, adenylate cyclase loses its responsiveness to ACTH but retains its ability to respond to catecholamines. This lack of responsiveness to ACTH by adenylate cyclase of mouse adipocyte plasma membrane can be overcome, at least partially, by addition of GPP (NH)p, an analog of GTP, to the assay medium. The data on mouse adipocyte membrane suggests that the coupling of ACTH receptor to adenylate cyclase is dependent on GTP and that catecholamine-activation of adenylate cyclase is less dependent on this nucleotide. The isolated intact white adipocyte of adult New Zealand rabbit responds to ACTH, but does not (or only weakly) respond to catecholamines. In contrast to the mouse plasma membrane preparation, adenylate cyclase of adipocyte membrane of the rabbit responds to ACTH. And the addition of GPP(NH)P is not required to demonstrate the CTH: sensitive adenylate cyclase activity. The difference between mouse and rabbit adipocyte membrane in the requirement for GPP(NH)P in ACTH action is not readily explained. The lack of catecholamine sensitivity of rabbit membrane enzyme cannot be reversed by addition of GPP(NH)P or adenosine deaminase. These two adenylate cyclase model systems using mouse and rabbit adipocyte plasma membrane may be useful tools for the study of the specificity and mechanism of action of lipolytic hormones such as ACTH and catecholamines.
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PMID:Response of white adipocyte of mouse and rabbit to catecholamines and ACTH. 2. Stability and restoration of activity of hormone-sensitive adenylate cyclase of adipocyte plasma membrane. 626 26

It has been suggested that part of the increased beta-catecholamine responsiveness in hyperthyroid animals is due to a decrease in alpha-catecholamine action. The present results indicate that neither hyperthyroidism nor hypothyroidism altered the alpha 2-adrenergic inhibition of adenylate cyclase or the alpha 1-adrenergic stimulation of phosphatidylinositol turnover in adipocytes from the white adipose tissue of hamsters. No effect of hyperthyroidism was found on the Kd for binding of [3H]dihydroergocryptine or the number of binding sites in membranes prepared from hamster adipocyte tissue. The stimulation of cyclic AMP due to beta-catecholamines was enhanced in adipocytes from hyperthyroid hamsters, as was lipolysis. However, in adipocytes from hyperthyroid hamsters the maximal stimulation of cyclic AMP due to isoproterenol, ACTH or epinephrine plus yohimbine, as seen in the presence of adenosine deaminase and theophylline, was less than in adipocytes from euthyroid hamsters. The activation of adenylate cyclase by isoproterenol was the same in membranes from hyperthyroid as compared to those from euthyroid hamsters in the absence or presence of guanine nucleotides. These data suggest that thyroid status has little effect on alpha-catecholamine action by enhances the activation of lipolysis by beta-catecholamine agonists.
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PMID:Effect of thyroid status on alpha- and beta-catecholamine responsiveness of hamster adipocytes. 627 17


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