The objective of this paper was to study the relaxant effect mechanism of an estrone derivative EA303 on isolated jejunum smooth muscle of rabbits.The sample was prepared with rabbit isolated jejunum smooth muscle, and the effect of EA303 on the spontaneous contraction of jejunum smooth muscle was investigated.The effect of EA303 on β-receptor was studied by observing the difference of relaxing concentration-response curves of EA303 pre-contracted with KCl or acetylcholine chloride before and after incubation with propranolol (0.1 μmol/L^-1).The influence of EA303 on the cumulative concentration-response curves of CaCl₂ was studied, and verapamil was used to compare with EA303 as a noncompetitive inhibitor of Ca²⁺ channel.EA303 (10-100 μmol/L^-1) significantly attenuated the tension and amplitude of spontaneous contraction of isolated jejunum smooth muscle.The relaxing concentration-response curves of EA303 pre-contracted by KCl or acetylcholine chloride significantly changed after incubation with propranolol (0.1 μmol/L^-1).The relaxing effect of EA303 induced by KCl was inhibited, but increased induced by acetylcholine chloride.Both incubation with EA303 (1, 3 μmol/L^-1) and verapamil (0.1 μmol/L^-1) shifted the concentration-response curves of CaCl₂ to the right, and the rightward shift of the concentration-response curves of CaCl₂ was dose-dependent with the decrease of maximum responses.EA303, similar to verapamil, had significant effect on contraction of the first phase and second phase induced by acetylcholine chloride.The relaxant effect of EA303 on jejunum smooth muscle had relationship with β-receptor, and EA303 could block calcium channel and inhibit the release of intracellular calcium.

Zhongnan Yaoxue

Relaxant effect of an estrone derivate EA303 on isolated descending colonic smooth muscle in rabbits

Author: Zhou, Qianqian ; Zhu, Lan ; Fu, Shouting ; Chen, Guoliang

The relaxant mechanism and effect of an estrone derivate EA303 on isolated descending colonic smooth muscle in rabbits were determinedThe sample was prepared by rabbit isolated descending colonic smooth muscle, and the possible mechanism was investigated.EA303 (10^-5-10^-4 mol/L^-1) significantly attenuated the tension and amplitude of spontaneous contraction of isolated descending colonic smooth muscle.The relaxing concentration-response curves of EA303 on preparations pre-contracted by BaCl₂ or KCl were significantly changed before and after incubation with glibenclamide (10^-5 mol/L^-1).Both incubations with EA303 (10^-6, 3 × 10^-6 mol/L^-1) and verapamil (10^-7 mol/L^-1) shifted the concentration-response curves of CaCl₂ to the right and the rightward shift of the concentration-response curves of CaCl₂ was dose-dependent with the maximum responses significantly decreased.EA303, similar to that produced by verapamil, had significant effect on contraction of Phase I and Phase II induced by ACh.The relaxant mechanism of EA303 on isolated descending colonic smooth muscle may be related to K⁺-ATP opening.EA303, like that produced by verapamil, could block the calcium channel and inhibit the release of intracellular calcium.

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Indication	Highest Phase	Country/Location	Organization	Date
Gastrointestinal Diseases	Discovery	China	Shenyang Pharmaceutical University	-

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