자궁평활근의 Carbachol 및 Oxytocin 수축에 있어서의 세포내 Ca²⁺ 동원

Intracellular Ca²⁺ Movement in Contraction Induced by Carbachol and Oxytocin in Rat Myometrium

The properties of cytosolic Ca²⁺ level([Ca²⁺]_i) movement of high KCl, carbachol and oxytocin were examined with myometrium isolated from non-pregnant rat(estrus cycle). High concentration of KCl≤23.3mM) induced rhythmic increases in [Ca²⁺]_i and muscle contraction. However, sustained [Ca²⁺]_i and contracion were obtained at higher KCl concentration (≥30.3mM) The rhythmic and sustained contraction closely associated with changes in [Ca²⁺]_i induced by high KCl. Carbachol (3 ~ 30μM generated rhythmic increases with tonic component in [Ca²⁺]_i and muscle contraction. Myometrial contraction stimulated by carbachol was also closely correlated with change in [Ca²⁺]_i. And the [Ca²⁺]_i/contraction relationships were similar when muscle strips were stimulated by high KCl and carbachol. Maximal concentration of carbachol (10μM) and oxytocin(100 nM) increased [Ca²⁺]_i and contraction which were slightly greater than that of high KCl in non-pregnant myometrium, respectively. However, the [Ca²⁺]_i and contraction were strongly inhibited by verapamil (10μM), a 1-type Ca²⁺ channel blocker, as in the case of high KCl. Additionally, although carbachol further increased [Ca²⁺]_i and contraction induced by high KCl, these changes also strongly inhibited by application of verapamil. These results suggest that uterotonic agents, carbachol and oxytocin, induced contraction by increase in [Ca²⁺]_i through Ca²⁺ influx than by a regulation of Ca²⁺-sensitization in non-pregnant myometrium.