Regulation of 5-hydroxytryptamine-induced calcium mobilization by cAMP-elevating agents in cultured canine tracheal smooth muscle cells.
The effects of increases in cellular adenosine 3'5'-cyclic monophosphate (cAMP) on 5-hydroxytryptamine-(5-HT-) induced generation of inositol phosphates (IPs) and increases in intracellular Ca2+ ([Ca2+]i) were investigated using canine cultured tracheal smooth muscle cells (TSMCs). Cholera toxin and forskolin induced concentration- and time-dependent cAMP formation with half-maximal effects (-logEC50) produced at concentrations of 7.0 +/- 0.5 and 4.9 +/- 0.4 respectively. Pretreatment of TSMCs with either forskolin or dibutyryl cAMP inhibited 5-HT-stimulated responses. Even after treatment for 24h, these agents still inhibited the 5-HT-induced Ca2+ mobilization. The inhibitory effects of these agents produced both depression of the maximal response and a shift to the right of the concentration response curves of 5-HT. The water-soluble forskolin analogue L-858051 [7-deacetyl-7beta-(gamma-N-methylpiperazino)-butyryl forskolin] significantly inhibited the 5-HT-stimulated accumulation of IPs. In contrast, the addition of 1,9-dideoxy forskolin, an inactive forskolin analogue, had little effect on this response. Moreover, SQ-22536 [9-(tetrahydro-2-furanyl)-9-H-purin-6-amine], an inhibitor of adenylate cyclase, and both H-89 [N-(2-aminoethyl)-5-isoquinolinesulphonamide] and HA-1004[N-(2-guanidinoethyl)-5-isoquinolinesulphonamide], inhibitors of cAMP-dependent protein kinase (PKA), attenuated the ability of forskolin to inhibit the 5-HT-stimulated accumulation of IPs. These results suggest that activation of cAMP/PKA was involved in these inhibitory effects of forskolin. The AlF4--induced accumulation of IPs was inhibited by forskolin, suggesting that G protein(s) are directly activated by AlF4-- and uncoupled from phospholipase C by forskolin treatment. These results suggest that activation of cAMP/PKA might inhibit the 5-HT-stimulated phosphoinositide breakdown and consequently reduce the [Ca2+]i increase or inhibit both responses independently.
Yang
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Cellular and Molecular Pharmacology Laboratory, Department of Pharmacology, Chang Gung College of Medicine and Technology, Kwei-San, Tao-Yuan, Taiwan.
Tsao
H L
HL
Chiu
C T
CT
Fan
L W
LW
Yu
S M
SM
D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D017607:Aluminum Compounds / Q000494:pharmacology; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002772:Cholera Toxin / Q000494:pharmacology; D005576:Colforsin / Q000031:analogs & derivatives / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004224:Diterpenes; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005459:Fluorides / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D016716:PC12 Cells; D051381:Rats; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology*; D013449:Sulfonamides; D014132:Trachea / Q000166:cytology
D017607:Aluminum Compounds; D004224:Diterpenes; D004791:Enzyme Inhibitors; D007546:Isoquinolines; D012702:Serotonin Antagonists; D013449:Sulfonamides; C055627:L 858051; C017759:9-(tetrahydro-2-furyl)-adenine; D005576:Colforsin; D012701:Serotonin; D003994:Bucladesine; D002772:Cholera Toxin; C043204:N-(2-guanidinoethyl)-5-isoquinolinesulfonamide; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D019204:GTP-Binding Proteins; D000225:Adenine; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; C047983:1,9-dideoxyforskolin; D005459:Fluorides; D002118:Calcium; C032311:aluminum fluoride