Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.5 (5'-nucleotidase)
 3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The regulation of adrenergic receptors in rat heart was measured in rats made hyperthyroid by injection with thyroxine and made hypothyroid by addition of propylthiouracil to the drinking water. Hyperthyroid rats display cardiac hypertrophy and a decrease in epididymal fat pad weight. The maximal beta-receptor level of ventricular membranes, as determined by (-)-[3H]dihydroalprenolol binding, was increased 60% by thyroxine treatment and decreased about 30% by propylthiouracil treatment. The affinity of the beta receptor was unchanged after thyroxine or propylthiouracil treatment. The maximal activity of the isoproterenol-stimulated adenylate cyclase (EC 4.6.1.1) varied with thyroid state in a manner parallel to the increase in beta-adrenergic binding sites. Thyroxine treatment also increases by 2-fold the beta receptors in isolated rat fat cells. Propylthiouracil treatment lowered the level of alpha receptors in heart by 30% as measured by [3H]dihydroergocryptine binding, but increased the affinity about 2.5-fold. The highest level of alpha receptors was seen in control hearts. These studies indicate that thyroxine may control the turnover of beta-adrenergic receptors in heart and fat cells and regulate physiological responses in these tissues via a hormone-hormone interplay system. Thyroxine treatment reduced the activity of the membrane-bound Mg2+-ATPase (EC 3.6.1.3) and 5'-mononucleotidase (EC 3.1.3.5) but appears to increase the activity of the (Na+ + K+)ATPase (EC 3.6.1.4).
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PMID:Hormone action at the membrane level. VIII. Adrenergic receptors in rat heart and adipocytes and their modulation by thyroxine. 14 63

The number of beta-adrenoceptors was measured in cardiac and renal cortex membranes from controls and thyroxine-treated rats. Two methods of membrane preparation (sucrose- and KCl-extraction) were compared. KCl-extraction yielded a higher number of beta-adrenoceptors, accompanied by increased activity of the plasma membrane enzyme marker 5'-nucleotidase. Thyroxine increased the number of beta-adrenoceptors in both cardiac and renal cortex membranes prepared with both methods. These results suggest that: i) Enrichment of the membrane fraction may explain the higher number of beta-adrenoceptors found with KCl, ii) Thyroid hormone plays a role in the regulation of beta-adrenoceptors in the renal cortex.
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PMID:Renal beta-adrenoceptors in thyroxine-treated rats. 133 Dec 24

1. Liver plasma membranes were isolated from control, propylthiouracil-induced hypothyroid and thyroxine-replaced rats; relative specific activities of 5'-nucleotidase were found to be similar, 5.6-6.1, demonstrating that comparable purity levels were achieved. 2. Radioligand binding studies indicated that hepatic alpha 1-, alpha 2- and beta-adrenergic receptor binding to control liver membranes was 1963.23 +/- 59.34, 77.64 +/- 2.20 and 111.18 +/- 11.04 fmol.mg-1, respectively. 3. Hypothyroidism induced a 67% and 54% decrease, respectively, in hepatic alpha 1- and alpha 2-adrenergic receptor binding with no change in beta-adrenergic receptor binding. 4. Thyroxine replacement achieved an 85% and 100% restoration, respectively, in hepatic alpha 1- and alpha 2-adrenergic receptor expression with no effect on the beta-adrenergic receptor.
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PMID:The impact of hypothyroidism and thyroxine replacement on the expression of hepatic alpha 1-, alpha 2- and beta-adrenergic receptors in rat liver plasma membranes. 284 17

1. Studies have shown that adenosine transport and adenosine A1 receptors in rat brain are subjected to regulation by thyroid hormone levels. Since the ectonucleotidase pathway is an important source of adenosine extracellular, in the present study the in vitro action of T3 and T4 hormones on ectonucleotidase activities in hippocampal synaptosomes was evaluated. 2. T3 (Triiodo-l-thyronine) significantly inhibited, in an uncompetitive manner, the ATP and ADP hydrolysis promoted by ATP diphosphohydrolase activity in hippocampal synaptosomes of adult rats. 3. In contrast, T4 (Thyroxine) only inhibited ATP hydrolysis in an uncompetitive mechanism, at the concentrations tested (100-500 microM), but at the same time did not affect ADP hydrolysis. 4. In the present study, we also investigate the in vitro effect of T3 and T4 on 5'-nucleotidase activity. However, there are no changes in the activity of this enzyme in the presence of T3 and T4 in the hippocampal synaptosomes of rats. 5. These results suggest that thyroid hormones could be involved in the regulation of ectonucleotidase activities, such as ecto-ATP diphosphohydrolase and ecto-ATPase, possibly exerting a modulatory role in extracellular adenosine levels.
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PMID:In vitro effects of thyroid hormones on ectonucleotidase activities in synaptosomes from hippocampus of rats. 1246 75