title: Beta-adrenergic potentiation of endoplasmic reticulum Ca(2+) release in brown fat cells.
abstract: We find that the adrenergic agonist isoproterenol increases intracellular Ca(2+) concentration ([Ca(2+)](i)) in cultured rat brown adipocytes. At the concentration used (10 microM), isoproterenol-induced Ca(2+) responses were sensitive to block by either alpha(1)- or beta-adrenergic antagonists, suggesting an interaction between these receptor subtypes. Despite reliance on beta-adrenoceptor activation, the Ca(2+) response was not due solely to increases in cAMP because, administered alone, the selective beta(3)-adrenergic agonist BRL-37344 or forskolin did not increase [Ca(2+)](i). However, increased cAMP elicited vigorous [Ca(2+)](i) increases in the presence of barely active concentrations of the alpha-adrenergic agonist phenylephrine or the P2Y receptor agonist UTP. Consistent with isoproterenol recruiting only inositol 1,4,5-trisphosphate (IP(3))-sensitive Ca(2+) stores, endoplasmic reticulum store depletion by thapsigargin blocked isoproterenol-induced Ca(2+) increases, but removal of external Ca(2+) did not. These results argue that increases in cAMP sensitize the IP(3)-mediated Ca(2+) release system in brown adipocytes.
authors.affiliation: Section of Neurobiology, Physiology, and Behavior, University of California, Davis, California 95616, USA.
authors.forename: Eric V
authors.initials: EV
authors.lastname: Leaver
authors.forename: Pamela A
authors.initials: PA
authors.lastname: Pappone
mesh_terms: D017667:Adipocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D002001:Adipose Tissue, Brown / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000322:Adrenergic Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004983:Ethanolamines / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology*; D011224:Prazosin / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D000322:Adrenergic Agonists; D000317:Adrenergic alpha-Antagonists; D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D004791:Enzyme Inhibitors; D004983:Ethanolamines; D018048:Receptors, Purinergic P2; C057368:BRL 37344; D019284:Thapsigargin; D011433:Propranolol; D007545:Isoproterenol; D002118:Calcium; D011224:Prazosin