Up-regulation of Rnd1 during pregnancy serves as a negative-feedback control for Ca2+ sensitization of contractile elements in rat myometrium.
We investigated the role of Rnd1, a member of the small GTP-binding Rho protein family, in the change in Ca(2+) sensitivity of contractile element in rat myometrium at estrus, gestation, and postpartum stages. In the permeabilized muscles, GTPgammaS or carbachol with GTP increased Ca(2+) sensitivity of contractile force in non-pregnant myometrium at the estrus stage, whereas these stimuli were ineffective in pregnant myometrium at day 21. After postpartum, the reduced Ca(2+) sensitization was recovered. Semi-quantitative RT-PCR analysis indicated that the expressions of RhoA, ROCKI, and ROCKII were not significantly different between non-pregnant and pregnant myometria. In contrast, the expression of Rnd1 was increased during the course of pregnancy, reaching a maximal at day 21, and rapidly declined after the delivery. On the other hand, Ca(2+) sensitization of contractile elements was decreased during the progress in gestation. These results suggest that Rnd1 may have an important role as a negative-feedback control of uterine contraction during gestation through the inhibition of RhoA-mediated increase in the Ca(2+) sensitivity of contractile elements.
Kim
Yoon-Sun
YS
Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Bunkyo-ku, 113-8657, Tokyo, Japan.
Kim
Bokyung
B
Karaki
Hideaki
H
Hori
Masatoshi
M
Ozaki
Hiroshi
H
D000222:Adaptation, Physiological; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D046508:Culture Techniques; D005246:Feedback; D005260:Female; D006706:Homeostasis / Q000502:physiology*; D007537:Isometric Contraction / Q000502:physiology; D009215:Myometrium / Q000502:physiology*; D049590:Postpartum Period / Q000502:physiology; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D015854:Up-Regulation / Q000502:physiology*; D014590:Uterine Contraction / Q000502:physiology*; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
C491771:Rnd1 protein, rat; D020741:rho GTP-Binding Proteins; D002118:Calcium