Characterization of the tissue‐level Ca2+ signals in spontaneously contracting human myometrium |
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Authors: | Gilles Bru‐Mercier Joanna E Gullam Steven Thornton Andrew M Blanks Anatoly Shmygol |
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Institution: | 1. Warwick Medical School, University of Warwick, , Coventry, UK;2. Medical School, University of Exeter, , Exeter, UK |
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Abstract: | In the labouring uterus, millions of myocytes forming the complex geometrical structure of myometrium contract in synchrony to increase intrauterine pressure, dilate the cervix and eventually expel the foetus through the birth canal. The mechanisms underlying the precise coordination of contractions in human myometrium are not completely understood. In the present study, we have characterized the spatio‐temporal properties of tissue‐level Ca2+]i transients in thin slices of intact human myometrium. We found that the waveform of Ca2+]i transients and isotonic contractions recorded from thin slices was similar to the waveform of isometric contractions recorded from the larger strips in traditional organ bath experiments, suggesting that the spatio‐temporal information obtained from thin slices is representative of the whole tissue. By comparing the time course of Ca2+]i transients in individual cells to that recorded from the bundles of myocytes we found that the majority of myocytes produce rapidly propagating long‐lasting Ca2+]i transients accompanied by contractions. We also found a small number of cells showing desynchronized Ca2+]i oscillations that did not trigger contractions. The Ca2+]i oscillations in these cells were insensitive to nifedipine, but readily inhibited by the T‐type Ca2+ channel inhibitor NNC55‐0396. In conclusion, our data suggest that the spread of Ca2+]i signals in human myometrium is achieved via propagation of long‐lasting action potentials. The propagation was fast when action potentials propagated along bundles of myocytes and slower when propagating between the bundles of uterine myocytes. |
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Keywords: | calcium signalling human myometrium uterine contractility spontaneous activity calcium channel inhibitors |
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