• Mohammed Alotaibi.
• Department of Physiology, College of Medicine, King Saud University, P.O Box 2925, Riyadh 11461, Saudi Arabia. Electronic address: mfalotaibi@ksu.edu.sa.
• Life Sci. 2018 Apr 15; 199: 151-157.

AimsGiven the importance of ATP in the control of uterine activity for successful labor and involution, this study was performed to measure the level of P2X7 receptors (P2X7Rs) in rat myometrium at different gestational stages and to investigate the mechanisms of ATP-induced uterine contraction.Materials And MethodsMyometrial tissues were obtained from rats at different gestational stages and the level of P2X7Rs was measured by ELISA. In other experiments, the effect of 1 mM ATP was tested on spontaneous contraction and the underlying mechanisms were investigated.Key FindingsP2X7Rs were expressed in nonpregnant uterine tissues, progressively increased throughout pregnancy, and markedly peaked during postpartum involution. ATP significantly increased the force of spontaneous contraction in all uterine strips from different gestational stages with marked increase during labor and postpartum. ATP could not maintain the force when external Ca2+ was removed. In addition, ATP was able to cause tonic transient contraction in the absence of external Ca2+.SignificanceP2X7Rs are functionally regulated and contributed to ATP-induced uterine contraction. The sensitivity of the myometrium to ATP increases as pregnancy progresses and it involves Ca2+ influx and Ca2+ release pathways. The clear effects of ATP on contractility suggest its physiological requirement for successful labor and postpartum involution.Copyright © 2018 Elsevier Inc. All rights reserved.

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