TY - JOUR
T1 - Pertussis toxin-sensitive G proteins influence nitric oxide synthase III activity and protein levels in rat heart
AU - Hare, Joshua M.
AU - Kim, Benjamin
AU - Flavahan, Nicholas A.
AU - Ricker, Kelly M.
AU - Peng, Xinqi
AU - Colman, Laurence
AU - Weiss, Robert G.
AU - Kass, David A.
N1 - Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 1998/3/15
Y1 - 1998/3/15
N2 - Inhibitory G protein activity (G(i)) and nitric oxide (NO) modulate muscarinic-cholinergic (MC) inhibition of cardiac β-adrenergic inotropic responses. We hypothesized that G(i) mediates MC-NO synthase (NOS) signal transduction. Isoproterenol (0.2-0.8 μg/min) and acetylcholine (1 μM) were administered to isolated perfused rat hearts pretreated with saline (controls; n = 8) or pertussis toxin (PT; 30 μg/kg intraperitoneally 3 d before study; n = 20). PT abrogated in vitro ADP-ribosylation of G(i) protein α subunit(s) indicating near-total decrease in G(i) protein function. Isoproterenol increased peak + dP/dt in both control (peak isoproterenol effect: +2,589 ± 293 mmHg/s, P < 0.0001) and PT hearts (+3,879 ± 474 mmHg/s, P < 0.0001). Acetylcholine reversed isoproterenol inotropy in controls (108 ± 21% reduction of +dP/dt response, P = 0.001), but had no effect in PT hearts. In controls, N(G)-monomethyl-L-arginine (100 μM) reduced basal +dP/dt, augmented isoproterenol +dP/dt (peak effect: +4,634 ± 690 mmHg/s, P < 0.0001), and reduced the MC inhibitory effect to 69 ± 8% (P < 0.03 vs. baseline). L-arginine (100 μM) had no effect in controls but in PT hearts decreased basal +dP/dt by 1,426 ± 456 mmHg/s (P < 0.005), downward-shifted the isoproterenol concentration-effect curve, and produced a small MC inhibitory effect (27 ± 4% reduction, P < 0.05). This enhanced response to NO substrate was associated with increased NOS III protein abundance, and a three- to fivefold increase in in vitro calcium-dependent NOS activity. Neomycin (1 μM) inhibition of phospholipase C did not reverse L-arginine enhancement of MC inhibitory effects. These data support a primary role for G(i) in MC receptor signal transduction with NOS in rat heart, and demonstrate regulatory linkage between G(i) and NOS III protein levels.
AB - Inhibitory G protein activity (G(i)) and nitric oxide (NO) modulate muscarinic-cholinergic (MC) inhibition of cardiac β-adrenergic inotropic responses. We hypothesized that G(i) mediates MC-NO synthase (NOS) signal transduction. Isoproterenol (0.2-0.8 μg/min) and acetylcholine (1 μM) were administered to isolated perfused rat hearts pretreated with saline (controls; n = 8) or pertussis toxin (PT; 30 μg/kg intraperitoneally 3 d before study; n = 20). PT abrogated in vitro ADP-ribosylation of G(i) protein α subunit(s) indicating near-total decrease in G(i) protein function. Isoproterenol increased peak + dP/dt in both control (peak isoproterenol effect: +2,589 ± 293 mmHg/s, P < 0.0001) and PT hearts (+3,879 ± 474 mmHg/s, P < 0.0001). Acetylcholine reversed isoproterenol inotropy in controls (108 ± 21% reduction of +dP/dt response, P = 0.001), but had no effect in PT hearts. In controls, N(G)-monomethyl-L-arginine (100 μM) reduced basal +dP/dt, augmented isoproterenol +dP/dt (peak effect: +4,634 ± 690 mmHg/s, P < 0.0001), and reduced the MC inhibitory effect to 69 ± 8% (P < 0.03 vs. baseline). L-arginine (100 μM) had no effect in controls but in PT hearts decreased basal +dP/dt by 1,426 ± 456 mmHg/s (P < 0.005), downward-shifted the isoproterenol concentration-effect curve, and produced a small MC inhibitory effect (27 ± 4% reduction, P < 0.05). This enhanced response to NO substrate was associated with increased NOS III protein abundance, and a three- to fivefold increase in in vitro calcium-dependent NOS activity. Neomycin (1 μM) inhibition of phospholipase C did not reverse L-arginine enhancement of MC inhibitory effects. These data support a primary role for G(i) in MC receptor signal transduction with NOS in rat heart, and demonstrate regulatory linkage between G(i) and NOS III protein levels.
KW - β-adrenergic receptor
KW - L-arginine
KW - Muscarinic receptor
KW - Myocardial contractility
KW - Phospholipase C
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U2 - 10.1172/JCI1012
DO - 10.1172/JCI1012
M3 - Article
C2 - 9502785
AN - SCOPUS:0032521132
VL - 101
SP - 1424
EP - 1431
JO - Journal of Clinical Investigation
JF - Journal of Clinical Investigation
SN - 0021-9738
IS - 6
ER -