Comparison of effects of external Ca2+ on antioxytocin actions of antispasmodics in ovariectomized and estradiol-treated rat uteri.

Effects of high potassium depolarization, carbachol and oxytocin on the lanthanum-resistant 45Ca fraction in rat myometrium.

“…The increase in the 45Ca space in the estrogenized myometrium, es pecially in the later phase, was much greater than that in the ovariectomized one. The greater increase in the 45Ca space by high-K+ in the later phase in the estrogenized uterus may be due to the fact that the Ca exchange ability in the estrogenized tissue is larger than that in the ovariectomized one (7). The contractile responses of the rat longitudinal muscle strips to the contractile agents used here reached their maximum within 10 min (data not shown).…”

“…Recently, Uruno et al (7) For measurement of the 45Ca tissue space, the excised uterine horns in Tris-buffered solution, bubbled continuously with 100% 02 at room temperature, were freed from fat and connective tissue; and the myometrial longitudinal muscle layers were separated as described previously (7). After equilibration with the oxygenated Tris-buffered solution for 60 min which was kept at 32'C, the muscle layer was incubated in the oxygen ated Tris-buffered solution (10 ml) containing 45Ca (0 .1 /iCi/ml) or 45Ca plus KCI (60 mM), carbachol (2X 10'6 and 2x10-4 M) or oxytocin (10'4, 10'3 and 10-2 units/ml) for given times (5, 15, 30 and 60 min) at 32°C.…”