Effects of acetylcholine on inositol 1,4,5-triphosphate formation in cervix uteri myometrial cells of human

To detect inositol 1,4,5-triphosphate (IP3) formation of pregnant and nonpregnant human myometrial cells induced by acetylcholine (ACh). [3H] IP3 competitive protein binding assay. Basal levels of IP3 in pregnant and nonpregnant human myometrial cells were (82 +/- 9) and (96 +/- 10) nmol.g-1 (protein), respectively (n = 6). Incubated with ACh 50 mumol.L-1 for 5 min, IP3 reached the peak levels (109 +/- 11) and (122 +/- 15) nmol.g-1 (protein), respectively (n = 6), but difference of the increments of IP3 in pregnant and nonpregnant women was not significant. The increased IP3 induced by ACh was inhibited by atropine (Atr) 1 mumol.L-1. The basal IP3 level in pregnant cervix myometrial cells was higher than that in nonpregnant women. ACh increased the IP3 formation.