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Oxytocin Inhibits T-Type Calcium Current of Human Decidual Stromal Cells

Institute of Cell Signalling (B.L., S.J.H.), University of Nottingham, Queens Medical Centre, Nottingham NG7 2UH, United Kingdom; and Centre for Reproduction and Early Life (R.N.K.), Institute for Clinical Research, University of Nottingham, Nottingham NG7 2RD, United Kingdom

Address all correspondence and requests for reprints to: Raheela N. Khan, Academic Division of Obstetrics and Gynaecology, University of Nottingham, The Medical School, Derby City General Hospital, Uttoxeter New Road, Derby DE22 3DT, United Kingdom. E-mail: raheela.khan{at}nottingham.ac.uk.

Context: Little is known about the crosstalk between the decidua and myometrium in relation to human labor. The hormone oxytocin (OT) is considered to be a key mediator of uterine contractility during parturition, exerting some of its effects through calcium channels.

Objective: The objective was to characterize the effect of OT on the T-type calcium channel in human decidual stromal cells before and after the onset of labor.

Design: The nystatin-perforated patch-clamp technique was used to record inward T-type calcium current (I_Ca(T)) from acutely dispersed decidual stromal cells obtained from women at either elective cesarean section [CS (nonlabor)] or after normal spontaneous vaginal delivery [SVD (labor)].

Setting: These studies took place at the University of Nottingham Medical School.

Results: I_Ca(T) of both SVD and CS cells were blocked by nickel (IC₅₀ of 5.6 µM) and cobalt chloride (1 mM) but unaffected by nifedipine (10 µM). OT (1 nM to 3.5 µM) inhibited I_Ca(T) of SVD cells in a concentration-dependent manner, with a maximal inhibition of 79.0% compared with 26.2% in decidual cells of the CS group. OT-evoked reduction of I_Ca(T) was prevented by preincubation with the OT antagonist L371,257 in the SVD but not CS group. OT, in a concentration-dependent manner, displaced the steady-state inactivation curve for I_Ca(T) to the left in the SVD group with no significant effect on curves of the CS group.

Conclusion: Inhibition of I_Ca(T) by OT in decidual cells obtained during labor may signify important functional remodeling of uterine signaling during this period.