Receptor-dependent G protein-mediated Ca2+ sensitization in canine airway smooth muscle.
To determine the mechanisms of receptor-dependent Ca2+ sensitization in airway smooth muscle, canine tracheal smooth muscle (CTSM) was permeabilized with alpha-toxin or beta-escin. Although the effects of 5-hydroxytryptamine (100 microM), histamine (100 microM), and the thromboxane A2 analogue U-46619 (100 microM) were negligible, carbachol (100 microM) and endothelin-1 (ET-1, 1 microM) evoked additional contractions of 47.0 +/- 5.90% and 25.0 +/- 5.37% (n = 6) at pCa 6.7 with GTP (3 microM) (normalized to the maximum contraction at pCa 4.5) in alpha-toxin-permeabilized CTSM. GDP-beta-S (1 mM) reversed the carbachol and ET-1 responses completely. GTP-gamma-S (30 microM) and 4 beta-phorbol 12,13-dibutyrate (PDBu, 3 microM) increased the Ca2+ sensitivity (median effective pCa) of contraction by 1.8- and 4.4-fold, respectively (n = 4-11, P < 0.05). The effects of saturating concentrations of GTP-gamma-S and PDBu were additive. A synthetic peptide (T2) corresponding to the actin-binding site of calponin caused a dose-dependent contraction of beta-escin permeabilized CTSM, with the peak effect (25 +/- 4%, n = 4) at 1200 microM, PDBu (3 microM) caused contraction of the T2 peptide-treated CTSM. In conclusion, Ca2+ sensitization of CTSM depends on receptor type and is mediated by G proteins and protein kinase C whose effects are additive, with a partial contribution by calponin.
Iizuka
K
K
First Department of Internal Medicine, Gunma University Faculty of Medicine, School of Medicine, Japan. Iizukak@sb.gunma-u.ac.jp
Dobashi
K
K
Yoshii
A
A
Horie
T
T
Suzuki
H
H
Nakazawa
T
T
Mori
M
M
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000535:Aluminum / Q000494:pharmacology; D000818:Animals; D001427:Bacterial Toxins / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002217:Carbachol / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D004285:Dogs; D019332:Endothelin-1 / Q000494:pharmacology; D004928:Escin / Q000494:pharmacology; D005260:Female; D005461:Fluorine / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006460:Hemolysin Proteins / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology; D007537:Isometric Contraction; D008297:Male; D008840:Microfilament Proteins; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000494:pharmacology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology; D013928:Thromboxane A2 / Q000031:analogs & derivatives / Q000494:pharmacology; D014132:Trachea / Q000033:anatomy & histology / Q000378:metabolism*; D000096985:Calponins
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000535:Aluminum; D001427:Bacterial Toxins; D002118:Calcium; D002135:Calcium-Binding Proteins; D002217:Carbachol; D019332:Endothelin-1; D004928:Escin; D005461:Fluorine; D019204:GTP-Binding Proteins; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006460:Hemolysin Proteins; D006632:Histamine; D008840:Microfilament Proteins; D010446:Peptide Fragments; D015240:Phorbol 12,13-Dibutyrate; D011450:Prostaglandin Endoperoxides, Synthetic; D011493:Protein Kinase C; D011976:Receptors, Muscarinic; D012701:Serotonin; D013928:Thromboxane A2; D000096985:Calponins; C021091:staphylococcal alpha-toxin; C053629:fluoroaluminum