Mechanical stretch up-regulates the human oxytocin receptor in primary human uterine myocytes

Terzidou V, Sooranna SR, Kim LU, Thornton S, Bennett PR, Johnson MR.
J Clin Endocrinol Metab. 2005 Jan;90(1):237-46

At the end of the pregnancy, the walls of the uterus contract marking the onset of labour, which become stronger and more coordinated as labour proceeds. The hormone oxytocin plays a role in this process, stimulating contractions and promoting labour. Concentrations of the oxytocin receptor on the surface of uterine muscle cells increase markedly at this time, enabling the uptake of oxytocin into uterine muscle cells and the initiation of labour. However, factors that promote the synthesis of oxytocin and regulate the expression of the oxytocin receptor on uterine muscle cells remain undefined.

In this study, the researchers investigated whether mechanical stretching of uterine muscle cells in late pregnancy increases concentrations of oxytocin receptors on the surfaces of uterine muscle cells, thus promoting the onset of labour. The researchers took biopsies from women who were in labour, who were pregnant but not in labour and who were not pregnant. Uterine muscle cells were collected from these tissue samples and cultured in the laboratory and were subjected to mechanical stretching using a computer-driven tension system. Proteins that might promote the synthesis of oxytocin and expression of the oxytocin receptor were also investigated.

The researchers found that mechanical stretching of cells from pregnant women who were not in labour promoted the expression of the oxytocin receptor on these cells. Increased stretch was also associated with increased activity of certain proteins that promote oxytocin synthesis and oxytocin receptor expression, particularly the transcription factor C/EBP.

These data add the oxytocin receptor to the range of proteins associated with contraction of human uterine muscle and suggest that stretch play a significant role in the upregulation of proteins that promote contraction before the onset of labour.

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