토끼 기관평활근 수축에서 G Protein의 역할

Role of G-protein in the Contraction of Rabbit Trachealis Muscle

Fluoride (F-), a known stimulator of G-protein, induced strong contraction in rabbit trachealis muscle. AlCl₃(5 ~ 20 μM), which is required for G-protein stimulation by F^-, potentiated the contractile response to F^-. Ca²⁺-removal and verapamil, a calcium channel blocker, inhibited the fluoroaluminate-induced contraction. Fluoroaluminate increased ⁴⁵Ca influx in the absence and presence of verapamil. In heparin-loaded muscle high K⁺-induced contraction was not affected, but acetylcholine and fluoroaluminate-induced contractions were inhibited. The fluoroaluminate-induced contraction was partially relaxed by isoproterenol, a stimulator of adenylate cyclase. Pertussis toxin partially inhibited fluoroaluminate-induced contraction and potentiated isoproterenol-induced relaxation in the presence of fluoroaluminate, but had no effect on acetylcholine-induced contraction and the isoproterenol-induced relaxation in the presence of acetylcholine. These results suggest that fluoroaluminate has the ability to stimulate at least two putative G-proteins in rabbit trachealis muscle; One causes Ca²⁺ influx through the potential-operated Ca²⁺ channel and the other induces intracellular Ca²⁺ release by the increase of inositol-1, 4, 5-triphosphate.