Abstract
Male Sprague-Dawley rats were subcutaneously injected with 2.5mg/kg phenylephrine or 2.5mg/kg isoproterenol or both (2.5mg/kg for each drug) for 4 days, twice a day. Samples of scapular brown adipose tissue (BAT) and epididymal white adipose tissue (WAT) were collected for the measurement of adrenomedullin (AM) levels and the gene expression of preproAM, calcitonin receptor like receptor (CRLR) and its activity modifying proteins (RAMPs) by radioimmunoassay and RT-PCR. These values were compared with those in the rats that received 0.9% saline. The gene expression of AM and AM receptor components in BAT are much less than that in epididymal WAT. In BAT there were an increase in AM peptide level after a combined treatment of alpha(1) and beta adrenoceptor agonists and increases in preproAM mRNA levels for rats treated with alpha(1) and beta receptor agonists alone or in combination. Both CRLR and RAMP2 mRNA levels of alphabeta group were increased significantly. In WAT, AM peptide level, RAMP1 and RAMP2 mRNA expression levels were augmented in the alpha group while CRLR mRNA level was enhanced in the beta group. The levels of AM, its receptor and RAMPs are much less in BAT than in WAT but adrenergic stimulation has a greater effect on the AM and its receptor components in BAT than those in WAT. AM stimulates lipolysis and increases the level of uncoupling protein-1 (UCP-1) in BAT. It may therefore enhance thermogenesis by increasing the availability of free fatty acids substrate as well as the UCP-1 level on the mitochondrial membrane.
MeSH terms
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Adipose Tissue, Brown / chemistry
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Adipose Tissue, Brown / drug effects*
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Adipose Tissue, Brown / metabolism
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Adipose Tissue, White / chemistry
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Adipose Tissue, White / drug effects*
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Adipose Tissue, White / metabolism
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Adrenergic Agents / administration & dosage
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Adrenergic Agents / pharmacology*
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Adrenomedullin / genetics
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Adrenomedullin / metabolism*
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Animals
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Blotting, Western
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Body Weight / drug effects
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Calcitonin Receptor-Like Protein
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Gene Expression Regulation / drug effects
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Injections, Subcutaneous
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Intracellular Signaling Peptides and Proteins / genetics
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Intracellular Signaling Peptides and Proteins / metabolism
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Ion Channels / metabolism
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Isoproterenol / administration & dosage
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Isoproterenol / pharmacology
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Lipolysis / drug effects
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Male
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Membrane Proteins / genetics
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Membrane Proteins / metabolism
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Mitochondrial Proteins / metabolism
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Phenylephrine / administration & dosage
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Phenylephrine / pharmacology
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Protein Precursors / genetics
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Protein Precursors / metabolism
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RNA, Messenger / genetics
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RNA, Messenger / metabolism
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Radioimmunoassay
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Rats
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Rats, Sprague-Dawley
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Receptor Activity-Modifying Proteins
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Receptors, Adrenomedullin
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Receptors, Calcitonin / genetics
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Receptors, Calcitonin / metabolism
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Receptors, Peptide / genetics
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Receptors, Peptide / metabolism*
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Reverse Transcriptase Polymerase Chain Reaction
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Uncoupling Protein 1
Substances
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Adrenergic Agents
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Calcitonin Receptor-Like Protein
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Intracellular Signaling Peptides and Proteins
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Ion Channels
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Membrane Proteins
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Mitochondrial Proteins
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Protein Precursors
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RNA, Messenger
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Receptor Activity-Modifying Proteins
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Receptors, Adrenomedullin
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Receptors, Calcitonin
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Receptors, Peptide
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Ucp1 protein, rat
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Uncoupling Protein 1
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preproadrenomedullin
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Adrenomedullin
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Phenylephrine
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Isoproterenol