Pertussis toxin-sensitive G(i)-proteins and intracellular calcium sensitivity of vasoconstriction in the intact rat tail artery.
1. We studied the involvement of pertussis toxin (PTX)-sensitive G-proteins in the sensitivity of arterial constriction to intracellular calcium ([Ca(2+)](i)) mobilization. 2. Vasoconstriction was measured in vitro in perfused, de-endothelialized rat tail arteries loaded with the calcium-sensitive dye, fura-2 and treated or not with PTX (30 - 1000 ng ml(-1)). Arteries were stimulated with noradrenaline (NA, 0.1 - 100 microM) or KCl (15 - 120 mM). 3. KCl elicited a smaller vasoconstrictor response (E(max)=94+/-8 mmHg) than NA (E(max)=198+/-9 mmHg) although [Ca(2+)](i) mobilization was similar (E(max)=123+/-8 and 135+/-7 nM for KCl and NA, respectively). PTX (1000 ng ml(-1)) had no effect on [Ca(2+)](i) mobilization but lowered NA- (but not KCl-) induced vasoconstriction (E(max)=118+/-7 mmHg). 4. G(i/o)-proteins were revealed by immunoblotting with anti-G(i alpha) and anti-G(o alpha) antibodies in membranes prepared from de-endothelialized tail arteries. [alpha(32)P]-ADP-ribosylation of G-proteins by PTX (1000 ng ml(-1)) was demonstrated in the intact rat tail artery (pixels in the absence of PTX: 3150, presence: 25053). 5. In conclusion, we suggest that smooth muscle cells possess a PTX-sensitive G(i)-protein-mediated intracellular pathway which amplifies [Ca(2+)](i) sensitivity of contraction in the presence of agonists such as NA.
Spitzbarth-Régrigny
E
E
Laboratoire de Pharmacologie Cardiovasculaire, UPRES EA 3116 Faculté de Pharmacie, UHP-Nancy 1, 5 rue Albert Lebrun, 54000 Nancy, France.
Petitcolin
M A
MA
Bueb
J L
JL
Tschirhart
E J
EJ
Atkinson
J
J
Capdeville-Atkinson
C
C
D000818:Animals; D001158:Arteries / Q000737:chemistry / Q000187:drug effects* / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D015151:Immunoblotting; D066298:In Vitro Techniques; D008297:Male; D008566:Membranes / Q000737:chemistry / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D037342:Pertussis Toxin; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013623:Tail / Q000098:blood supply; D014661:Vasoconstriction / Q000187:drug effects*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D010566:Virulence Factors, Bordetella; D011189:Potassium Chloride; D037342:Pertussis Toxin; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D002118:Calcium; D009638:Norepinephrine