Ca2+ sensitivity of skinned uterine muscle fibers in unilaterally pregnant rats.
We prepared chemically skinned uterine muscle fibers from both horns of unilaterally pregnant rats and investigated the effect of gestation on the Ca2+ sensitivity of the Ca(2)-induced contraction. The Ca2+ sensitivity was defined as the pCa (minus logarithm of free calcium concentration) required for half maximum activation of force production. Gravid horns did not show any statistical difference in the Ca2+ sensitivity between normal pregnant and unilaterally pregnant rats. Non-gravid horns of unilaterally pregnant rats before Day 14 of gestation showed the same behavior in the Ca2+ sensitivity as horns of normal pregnant rats. After Day 15 of gestation the Ca2+ sensitivity of non-gravid horn also increased but significantly less than that of gravid horn. Taking into account the hormonal situation, the present results suggest that some local factors, such as an increased size of conceptus (fetus and placenta) and/or intercellular binding conditions of myometrium modulated by the gap junction formation and the appearance of connexin molecules, may also be requisite for the regulation of the contractile activity associated with parturition and delivery of the fetus and placenta.
Department of Obstetrics & Gynecology, Jikei University School of Medicine, Tokyo, Japan.
K
K
Ochiai
K
K
Ohura
M
M
Nakano
K
K
Sakihira
Y
Y
Shimizu
Y
Y
Terashima
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D005260:Female; D005865:Gestational Age; D066298:In Vitro Techniques; D007743:Labor, Obstetric; D009130:Muscle, Smooth / Q000187:drug effects*; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D014590:Uterine Contraction / Q000187:drug effects*; D014599:Uterus / Q000187:drug effects
D002118:Calcium