Beta-adrenergic receptor gene expression in bovine skeletal muscle cells in culture

• Published in: Journal of animal science Vol. 76; no. 9; pp. 2382 - 2391
• Main Authors: Bridge, K.Y, Smith, C.K. II, Young, R.B
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Savoy, IL Am Soc Animal Sci 01.09.1998; American Society of Animal Science; Oxford University Press
• Subjects: Adrenergic beta-Agonists - pharmacology; Animals; beta-adrenergic receptors; binding; Biological and medical sciences; Cattle; Cattle - genetics; Cattle - metabolism; cell lines; Cell receptors; Cell structures and functions; Cells, Cultured; cyclic AMP; Cyclic AMP - biosynthesis; dexamethasone; Dexamethasone - pharmacology; Female; fibroblasts; Fibroblasts - cytology; Fibroblasts - metabolism; Fundamental and applied biological sciences. Psychology; gene expression; Gene Expression Regulation - drug effects; Genetics; Glucocorticoids - pharmacology; isoprenaline; Isoproterenol - pharmacology; Molecular and cellular biology; Monoamines receptors (catecholamine, serotonine, histamine, acetylcholine); Muscle, Skeletal - cytology; Muscle, Skeletal - embryology; Muscle, Skeletal - metabolism; Muscular system; myosin; Myosin Heavy Chains - analysis; Myosin Heavy Chains - biosynthesis; nuclei; Pregnancy; Receptors, Adrenergic, beta - biosynthesis; Receptors, Adrenergic, beta - genetics; RNA; RNA, Messenger - analysis; skeletal muscle; tissue culture; Up-Regulation; Zoology; Cell culture; Membrane receptor; Vertebrata; Mammalia; Bovine; Plasma membrane; Myoblast; Artiodactyla; Gene expression; Ungulata; Biological receptor; β-Adrenergic receptor
• ISSN: 0021-8812; 1525-3163; 0021-8812
• DOI: 10.2527/1998.7692382x

Beta-adrenergic receptors (betaAR) are abundant in fetal, neonatal, and adult skeletal muscles of cattle; however, only minimal levels of functional betaAR were detected in multinucleated muscle cell cultures prepared from 90- to 150-d fetal bovine skeletal muscle. Two other lines of evidence were consistent with low levels of betaAR expression in bovine muscle cultures. First, treating the cells with 10-6 M isoproterenol for up to 20 mm did not increase intracellular cAMP concentration. Second, neither the quantity of myosin heavy chain (MHC) nor its apparent synthesis rate were changed by treating the cells for 4 d with 10-7 or 10-6 M isoproterenol. Despite these results, the mRNA for the beta2AR could be detected in muscle cultures by PCR and on slot blots. Thus, the beta2AR mRNA was expressed, but significant levels of functional receptors could not be detected. Glucocorticoids are known to activate expression of betaAR genes in several tissues, and the effect of dexamethasone on beta AR gene expression in bovine multinucleated muscle cell cultures was evaluated. The intracellular concentration of cAMP following treatment with isoproterenol was elevated 10-fold by dexamethasone, and the population of functional receptors was elevated by approximately 50%. The effect of dexamethasone on muscle protein synthesis and accumulation was analyzed after pretreating the cells with dexamethasone for 24 h, followed by treatment with dexamethasone and 10-6 M isoproterenol for an additional 48 h. The quantity of MHC synthesized and the apparent synthesis rate of MHC were stimulated by 10 to 35%. These effects seem to be due to posttranscriptional events, because the quantity of beta2AR receptor mRNA on slot blots was not increased by treatment with dexamethasone. Results of this study emphasize the importance of verifying that muscle cells contain functional betaAR when they are used to study the effects of betaAR agonists on muscle protein metabolism.