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:4.1.1.17 (ornithine decarboxylase)
6,351 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A mixture containing glucagon and thyroid hormone was previously devised that enhances markedly nuclear DNA replication and mitosis in the parenchymal liver cells of the unoperated rat. It is now shown that the glucagon of the stimulatory solution can be completely replaced by a mixture of a butyryl derivative of cyclic adenosine 3':5'-monophosphate and theophylline. Cyclic guanosine 3':5'-monophosphate and its butyryl derivatives and insulin and high levels of glucose are inactive. The inactivity of N2-monobutyryl cyclic guanosine 3':5'-monophosphate cannot be ascribed to rapid breakdown in the animal or to the impenetrability of the liver cell since the coumpound elevates the rate of hepatic amino acid transport and the activity of ornithine decarboxylase. The observation of others (MacManus, J.P., Franks, D.J., Youdale, T. & Braceland, B.M. (1972) Biochem. Biophys. Res. Commun. 49, 1201-1207) that the level of cylcic adenosine 3':5'-monophosphate is raised during most of the prereplicative period after 70% hepatectomy is confirmed. The evidence supports a positive role for adenosine 3':5-monophosphate in regulating DNA synthesis in the liver.
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PMID:Cyclic adenosine 3':5'-monophosphate and the induction of deoxyribonucleic acid synthesis in liver. 16 78

TSH (1.0 U im) caused a 22-fold increase in thyroidal ornithine decarboxylase activity (ODC) 6 hours after administration in intact rats. Hypophysectomized rats treated with 1 U TSH showed a 5-fold increase in thyroid ODC activity. This stimulation appeared to be specific for TSH since hormones known to induce ODC activity in other target tissues, such as ACTH or LH, showed no significant stimulation. DIBUTYRYL CYCLIC AMP and aminopylline caused a 12-fold increase in ODC activity 5 hours after administration. Prostaglandins have also been implicated in the TSH-induced stimulation of cyclic AMP. Indomethacin (1.0 mg/100 g body wt, ip), an inhibitor of prostaglandin synthesis, was administered 3 hours before TSH with a resulting 30% diminution (P less than .001) in ODC activity compared with the administration of TSH alone. To rule out the possibility that the increase in ODC activity with TSH might be due to increased thyroid hormone secretion, ODC activity was evaluated 6 hours after triiodothyronine administration (60 mug/100 g body wt), and no significant increase in thyroid ODC activity was found. Stimulation of ODC activity was 90% inhibited by the intraperitoneal administration of actinomycin D (80 mug/100 g body wt) or cycloheximide (400 mug/100 g body wt) given simultaneously with TSH. These results indicated that TSH specifically stimulated thyroid ODC activity, which may be important for the growth-promoting action of the hormone on the thyroid gland. This action may be mediated by cAMP and prostaglandins and may require new protein synthesis.
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PMID:Thyroid-stimulating hormone regulation of ornithine decarboxylase activity in the thyroid. 17 Nov 42

We studied the effect of thyroid hormone administration on responsivity of murine thyroid to exogenous thyrotropin (TSH) in order to explore the possibility that the thyroid gland might be directly inhibited by its own hormones. In the rat both L-thyroxine (T4) and 3,5,3'-L-triiodothyronine (T3) pretreatment inhibited TSH-induced thyroidal ornithine decarboxylase (ODC) activity in vivo in a dose-related manner (half-maximal inhibition, 1.7 mug/rat and 0.6 mug/rat, respectively). Other structurally related compounds exhibited the following inhibitory potencies compared to T4: T3, 283%; triiodothyroacetic acid, 40%; D-T4, 18%; 3,5-L-diiodothyronine, 9%. Monoiodotyrosine, diiodotyrosine, and iodide were not inhibitory. The full inhibitory effect of T4 or T3 was observed when thyroid hormone was administered from 96 to 12 h before TSH and was also seen in hypophysectomized animals. Pretreatment with T4 or T3 in divided doses over 2 1/2 days inhibited TSH-induced increase in [1-14C]glucose oxidation to 14C02 and [3H] leucine incorporation into protein in rat thyroid. In the mouse T4 or T3 pretreatment (0.25-25 mug daily) caused dose-related inhibition of both thyroidal ODC activity and 131I release induced by TSH in vivo. In mice on a low-iodine diet (LID) but not in animals on a regular diet (RD) NaI pretreatment also blunted TSH-induced thyroidal ODC activation and 131I release. When LID or RD mice were pretreated with 12.5-125 mug of T4 or T3 over 2 1/2 days, TSH-induced in vitro stimulation of thyroid cyclic 3',5'-adenosine monophosphate formation was inhibited in a dose-related manner; NaI pretreatment was inhibitory in the LID mouse only. Prior administration of exogenous TSH blunted the activation of thyroid ODC and thyroid hormone release induced by subsequent TSH administration in rat and mouse. These studies indicate altered thyroid responsivity to TSH under the influence of circulating thyroid hormones and suggest the existence of a "short-loop" negative feedback regulating thyroid function.
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PMID:Altered thyroidal responsivity to thyrotropin induced by circulating thyroid hormones. A "short-loop" regulatory mechanism? 17 94

The purpose of this study was to elucidate the mechanism by which thyroid hormone alters urea synthesis. A set of three experiments was investigated in three groups of rats given 6-propyl-2-thiouracil (a thyroid inhibitor) without triiodothyronine treatment, treated with 6-propyl-2-thiouracil plus triiodothyronine or neither 6-propyl-2-thiouracil nor triiodothyronine (control). We attempted to determine whether the concentration of ornithine and N-acetylglutamate regulated urea synthesis and whether activities of two ornithine-catabolizing enzymes accounted for changes in ornithine concentration. Urinary excretion of urea and the liver concentration of N-acetylglutamate and ornithine in rats given 6-propyl-2-thiouracil plus triiodothyronine were significantly lower than in rats given 6-propyl-2-thiouracil alone. The liver concentration of N-acetylglutamate was correlated to urea excretion (r = 0.911, P less than 0.001). The activities of carbamylphosphate, synthetase, ornithine aminotransferase and ornithine decarboxylase in liver of the group treated with 6-propyl-2-thiouracil alone were significantly lower than those of the 6-propyl-2-thiouracil plus triiodothyronine-treated group. The results suggest that a higher liver concentration of N-acetylglutamate and ornithine in the hypothyroid (6-propyl-2-thiouracil only) rats is likely to stimulate urea synthesis. The thyroid hormone-induced increase in activities of ornithine catabolizing enzymes may be primarily responsible for changes in ornithine concentration.
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PMID:Changes in liver concentration of N-acetylglutamate and ornithine are involved in regulating urea synthesis in rats treated with thyroid hormone. 156 67

In mature animals, thyroid hormone produces parallel up-regulation of beta-adrenergic receptor binding sites and their linkage to adenylate cyclase; during development, these same processes may be critical in establishing the set-point for subsequent adrenergic reactivity. In the current study, we administered triiodothyronine to neonatal rats for the first five days postpartum and evaluated [125I]pindolol binding capabilities and adenylate cyclase activity in membrane preparations from heart and kidney. In the heart, hyperthyroidism elicited an initial increase in receptor density, with subsequent deficits and an eventual return to normal values by young adulthood. In contrast, the ability of isoproterenol, a beta-adrenergic agonist, to stimulate adenylate cyclase was enhanced regardless of whether receptor numbers were increased or decreased; the same effects were also present for basal adenylate cyclase activity and non-receptor-mediated stimulation by forskolin. Enhanced cyclase activity involved both increases in the magnitude of response as well as accelerated onset of the postweaning peak of enzyme activity, results which suggest a direct impact of thyroid status on the ontogenetic expression of adenylate cyclase itself. The kidney, which possesses less efficient beta-receptor coupling to adenylate cyclase in the neonate, was less drastically affected by triiodothyronine for either beta-receptor binding sites or enzyme activity. As we had previously shown that neonatal hyperthyroidism uncouples beta-receptors from growth-related enzymes, such as ornithine decarboxylase, we also evaluated whether the promotion of adenylate cyclase responses was mechanistically linked to effect on ornithine decarboxylase; administration of cyclic AMP analogs to 5 days-old rats led to inhibition of the enzyme in the heart, whereas the same treatment in 9 days-old animals was ineffective. These data suggest that thyroid hormone differentially regulates the development of beta-receptors as well as adenylate cyclase and ornithine decarboxylase, with preferential effects on tissues, such as the heart, that already possess efficient linkage of the receptors to cell transduction mechanisms at birth.
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PMID:Thyroid hormone differentially regulates development of beta-adrenergic receptors, adenylate cyclase and ornithine decarboxylase in rat heart and kidney. 166 5

The ornithine decarboxylase-inducing factor (ODC factor) was purified about 1,000-fold in 42% yield from the ascites fluids of an Ehrlich ascites tumor by a combination of centrifugation and concanavalin A (ConA) treatment. A single ip injection of 0.5 micrograms of the purified factor per mouse resulted in half-maximum induction of liver ODC. The factor was found to be a trypsin- and chymotrypsin-resistant, acidic glycoprotein (pI about 4.43) with a minimum molecular weight of about 70 kilodaltons, containing a disulfide bond(s) in its functional domain. It did not react with ConA. This factor induced retrodifferentiation of liver function, causing a marked increase of prototype M2 isozyme of pyruvate kinase. It reduced liver catalase activity, and also modified thyroid hormone metabolism, reducing the serum levels of T4 and T3. These results suggest that the ODC factor is multifunctional and induces many of the changes observed in a tumor-bearing host.
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PMID:Purification of ornithine decarboxylase-inducing factor from cell-free ascites fluid of Ehrlich ascites tumor and its characteristics. 170 56

The role of thyroid status in the ontogeny of beta adrenergic receptor control of ornithine decarboxylase (ODC) activity was assessed in hearts and kidneys of neonatal rats. Hyperthyroidism induced by administration of tri-iodothyronine on postnatal days 1 to 5 caused a reduction in the ability of isoproterenol to stimulate cardiac ODC but subsequently accelerated the onset of the postweaning peak of the response; the latter effect was even more prominent when tri-iodothyronine administration was given on postnatal days 14 to 18. Hypothyroidism induced by propylthiouracil administration led to persistent subsensitivity of the cardiac ODC response to beta receptor stimulation. Kidney ODC, which does not become subject to beta receptor regulation until after weaning, was resistant to hyperthyroid-induced changes in reactivity, but hypothyroidism still resulted in long-term response deficits. These results suggest that thyroid hormone is permissive for normal development of the beta receptor-ODC link, and that the euthyroid state provides the optimal conditions for maturation of this signal transduction mechanism. The relative resistance of kidney ODC responses to alterations by hyperthyroidism further indicates that the effects of excess hormone can only be expressed when the receptor-enzyme link is already competent. Finally, thyroid status had equivalent effects on the abilities of vasopressin or angiotensin to stimulate ODC, suggesting that the site of thyroid hormone action is at a transduction locus common to several different receptor types.
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PMID:Role of thyroid hormone in the development of beta adrenergic control of ornithine decarboxylase in rat heart and kidney. 184 10

The binding of 3,5,3'-L-triiodothyronine (T3) and thyroxine (T4) on liver nuclear receptors and the activity of malic enzyme and ornithine decarboxylase was examined in infantile rats aged in 1, 3, 7, 23, 29 days and in adult rats. No changes in the affinity constants (Ka) of nuclear receptors were observed for T3 or T4. The maximum binding capacity (MBC) estimated with the use of Scatchard plot analysis was unchanged for T3, the highest MBC for 125I-T4 being noted in rats aged 7 days. Malic enzyme activity in rat liver during the first three neonatal weeks was almost undetectable, but markedly increased on the 29th day. Ornithine decarboxylase activity was found to be significantly higher on the first day after birth as compared with that of the remaining age groups. The findings indicate that the thyroid hormone-nuclear receptor complex in rat liver does not seem to be sufficient for the induction of these enzymes in postnatal period of life.
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PMID:Nuclear binding of thyroid hormones and activity of malic enzyme and ornithine decarboxylase in rat liver during postnatal development. 209 77

Diabetes mellitus causes a more profound reduction of left ventricular weight (LVW) in the spontaneously hypertensive rat (SHR) than it does in nonhypertensive strains. Diabetes also depresses the activity of cardiac ornithine decarboxylase (ODC), an index of cell growth. We measured ODC activity, of ventricular homogenates obtained from diabetic SHR and nonhypertensive WKY rats, with and without chronic treatment with insulin or triiodothyronine (T3). Left ventricular ODC activities of nondiabetic SHR and WKY rats were not different from each other. Streptozotocin-induced diabetes (8 weeks) reduced left ventricular ODC activity of SHR and WKY rats to the same extent; the effect was characterized by a reduction in apparent Vmax with no change in apparent Km. Both T3 and insulin therapy prevented the decline in ventricular ODC activity in both strains, although only the effect of insulin was correlated with LVW. The results suggest that the effects of diabetes on LVW and ODC activity are independent of attendant reductions in serum thyroid hormone levels. However, the results did not reveal any strain-selective effects of diabetes on ODC activity which might have contributed to the pronounced loss of LVW in the SHR strain.
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PMID:Cardiac ornithine decarboxylase of diabetic spontaneously hypertensive rat: effects of insulin and thyroid hormone treatment. 214 35

Myocardial phosphorylase alpha activity responds to stimulation by catecholamines and thyroid hormone. In hyperthyroidism this enzyme is supersensitive to beta-adrenergic stimulation and blockade, indicating that its increased activity is an indirect effect of thyroid hormone. Myocardial ornithine decarboxylase (ODC) activity also responds to catecholamine and thyroid hormone stimulation. In the present studies, we sought to determine whether ODC shares the responses of phosphorylase alpha in hyperthyroidism. As opposed to euthyroid rats, isoproterenol acutely inhibited myocardial OCD activity in hyperthyroid rats. Timolol (60 mg/kg) injected immediately before the isoproterenol blocked this paradoxical inhibitory effect, defining it as beta-adrenergic. When timolol (100 mg/kg), distributed over a 24-h period, was administered during the 3 days of triiodothyronine (T3) administration, it blocked the T3 stimulation of myocardial OCD activity by 35%. However, timolol affected weight gain of the hyperthyroid rats. When fasted rats were used, timolol was without effect on T3-induced myocardial ODC stimulation. Timolol was also without effect on T3-induced stimulation of hepatic ODC or on T3-induced cardiomegaly. Timolol did decrease the T3-induced tachycardia. In summary, in the hyperthyroid heart, 1) isoproterenol paradoxically inhibits myocardial ODC activity and 2) timolol, when food intake is not a variable, is without effect. We conclude that the effect of thyroid hormone on myocardial ODC is not mediated by change in catecholamine sensitivity. Thus the behavior of phosphorylase alpha does not represent a general enzymatic phenomenon.
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PMID:Catecholamine-thyroid hormone interaction on myocardial ornithine decarboxylase. 712 44


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