Turkish Journal of Medical Sciences




The aim of this study was to evaluate influences of hormonal changes during rat estrous cycle on airway responsiveness to bronchoconstrictor and bronchodilator agents. Materials and methods: The study was performed in 5 groups of rat tracheal smooth muscle obtained during proestrus, estrus, metestrus, and diestrus phases of the estrous cycle, as well as the ovariectomized group (n:8/group). Cumulative acetylcholine contractions ranging from 10^{-8} to 10^{-3} M bath doses and the cumulative isoproterenol relaxations ranging from 10^{-8} to 10^{-3} M precontracted with 10^{-5} M of acetylcholine were recorded on isolated tracheas placed in a computerized tissue bath system. Results: Acetylcholine-induced contractions ranging from 10^{-5} to 10^{-3} M were significantly enhanced dose-dependently in tracheal smooth muscle from estrus rats compared to those from metestrus and ovariectomized rats. The relaxation induced by isoproterenol (10^{-8} -10^{-3} M) also significantly increased in tracheal smooth muscle precontracted with acetylcholine (10^{-5} M) taken from estrus rats. However, acetylcholine-induced contractility increase in tracheal smooth muscle was much more prominent than isoproterenol-induced relaxations in tracheal smooth muscle from estrus rats. Conclusion: These findings indicated that changes in estrogen and/or progesterone levels during rat estrous cycle might affect acetylcholine and isoproterenol sensitivity of the tracheal smooth muscle.


Acetylcholine, estradiol, estrous cycle, isoproterenol, tracheal smooth muscle

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