title: The effect of estrogen on passive length-tension relationship in the uterus of ovariectomized progesterone-treated pregnant rats.
abstract: Passive length-tension curves of uterine strips obtained on day 20 of pregnancy from ovariectomized, progesterone-treated (OVX-P), progesterone + estrogen-treated (OVX-PE), and intact pregnant rats (control) were determined, and the effects of ovarian hormones on the length of the collagenous framework (LZ), tension at in vivo length (TV), and distensibility (D) of the strips, which were obtained from the curves, were evaluated. LZ of circular strips, but not of longitudinal strips, of OVX-P rats was smaller than the in situ length (20 mm) of the strips, whereas the value of control rats was greater than 20 mm; TV of these strips was 4.5-fold of controls. Treatment with estrogen restored both LZ and TV to the control levels. D of both longitudinal and circular strips of OVX-P rats was smaller than the controls, estrogen increased D to longitudinal direction predominantly. Examination in Ca-free Tyrode's had no influence on any of LZ, TV or D. Results suggest that estrogen with progesterone develops the collagenous framework of the connective tissue to radial direction and distensibility of the uterine wall mainly to longitudinal direction, and thereby maintains the tension of the uterine wall to accommodate the product of conception in the rat.
mesh_terms: D000818:Animals; D002369:Castration; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D009215:Myometrium / Q000187:drug effects; D009929:Organ Size; D011247:Pregnancy; D011374:Progesterone / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D014590:Uterine Contraction / Q000187:drug effects*; D014599:Uterus / Q000187:drug effects*
chemical_list: D011374:Progesterone; D004958:Estradiol