title: Activation of lipolysis and cyclic AMP accumulation in rabbit adipocytes by isoproterenol in the presence of forskolin or pertussis toxin.
abstract: Adipocytes from rabbits are relatively insensitive to catecholamines or forskolin. However, the combination of catecholamines plus forskolin increased cyclic AMP accumulation and lipolysis much more than either agent alone. Pertussis toxin treatment also restored sensitivity to catecholamines. No defect in activation by catecholamines of adenylate cyclase was seen in isolated membranes incubated in the presence of GTP. Rabbit adipocytes appear to have an excess of the inhibitory guanine nucleotide binding protein (Ni). However, in plasma membranes this protein appeared to be relatively inactive as there was an activation of adenylate cyclase activity by catecholamines in the presence of GTP. These data suggest that in intact rabbit adipocytes catecholamines and forskolin are ineffective as stimulators of adenylate cyclase due to an excess of inhibitory guanine nucleotide binding proteins.
mesh_terms: D000243:Adenosine Deaminase / Q000378:metabolism; D037361:Adenylate Cyclase Toxin; D000273:Adipose Tissue / Q000187:drug effects* / Q000378:metabolism; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000818:Animals; D001427:Bacterial Toxins / Q000494:pharmacology*; D005576:Colforsin; D000242:Cyclic AMP / Q000378:metabolism*; D004224:Diterpenes / Q000494:pharmacology*; D004357:Drug Synergism; D005260:Female; D005990:Glycerol / Q000378:metabolism; D006150:Guanine Nucleotides / Q000494:pharmacology; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology*; D008066:Lipolysis / Q000187:drug effects*; D037342:Pertussis Toxin; D011817:Rabbits; D013806:Theophylline / Q000378:metabolism; D010566:Virulence Factors, Bordetella
chemical_list: D037361:Adenylate Cyclase Toxin; D001427:Bacterial Toxins; D004224:Diterpenes; D006150:Guanine Nucleotides; D010566:Virulence Factors, Bordetella; D005576:Colforsin; D000324:Adrenocorticotropic Hormone; D013806:Theophylline; D000242:Cyclic AMP; D037342:Pertussis Toxin; D000243:Adenosine Deaminase; D007545:Isoproterenol; D005990:Glycerol