title: Effect of ovarian steroid hormones on superficial activator calcium in the rabbit uterus.
abstract: Effect of oestradiol (E2) and progesterone (P) on activator calcium binding was studied in the rabbit uterus. Superficial Ca-binding of isolated uterine strips was characterized by determining the rate of loss of isometric tension evoked by low (2.4 V/cm) field strength electrical stimulation in Ca-free Krebs solution. Intramuscular injection of 10 mg P increased superficial Ca-binding significantly in the postpartum and E2-treated virgin uterus with a latency period of 8--12 hours. Bilateral ovariectomy on the 25th day of pregnancy decreased superficial Ca-binding progressively, which could be avoided by P-substitution. 72 hours after ovariectomy P-treatment failed to increase Ca-binding. Local application of cycloheximide increased Ca-binding in the E2-treated virgin uterus. The results suggest that a high P-level plays an important role in the induction and maintenance of a strong binding of superficial activator calcium in the rabbit uterus. Progressive disappearance of the strong binding near term and after bilateral ovariectomy correlates well with P-withdrawl in this species.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002369:Castration; D003513:Cycloheximide / Q000494:pharmacology; D004558:Electric Stimulation; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D049590:Postpartum Period; D011247:Pregnancy; D011374:Progesterone / Q000494:pharmacology*; D011817:Rabbits; D014590:Uterine Contraction / Q000187:drug effects*; D014599:Uterus / Q000378:metabolism*
chemical_list: D011374:Progesterone; D004958:Estradiol; D003513:Cycloheximide; D002118:Calcium