{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,20]],"date-time":"2026-01-20T14:26:49Z","timestamp":1768919209786,"version":"3.49.0"},"reference-count":32,"publisher":"American Physiological Society","issue":"2","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["American Journal of Physiology-Endocrinology and Metabolism"],"published-print":{"date-parts":[[1999,2,1]]},"abstract":"<jats:p> Oxytocin is commonly used to induce or augment labor, but its mode of action is uncertain. To address the issue, isometric tension and the intracellular free Ca<jats:sup>2+<\/jats:sup> concentration ([Ca<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub>) were simultaneously recorded from isolated strips of pregnant human myometrium loaded with fura 2. The changes in [Ca<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub>and tension during phasic contractions were indistinguishable in myometrium taken before or after the onset of labor, enabling samples to be pooled. Oxytocin (10 nM) had no effect on basal [Ca<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub>or tension, but it increased both the [Ca<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub>and the tension recorded during phasic contractions. Analysis of the [Ca<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub>-tension relationship revealed that during the falling (relaxation) phase of the contractile response, oxytocin increased the tension recorded at each [Ca<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub>. By manipulating extracellular Ca<jats:sup>2+<\/jats:sup>during phasic contractions, it was possible to ensure that the [Ca<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub>signals were similar in the presence and absence of oxytocin, yet oxytocin still improved the [Ca<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub>-tension relationship. We conclude that 10 nM oxytocin increases the [Ca<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub>sensitivity of the contractile proteins only after a contraction has begun, possibly by causing inhibition of myosin light chain phosphatase. <\/jats:p>","DOI":"10.1152\/ajpendo.1999.276.2.e345","type":"journal-article","created":{"date-parts":[[2017,12,22]],"date-time":"2017-12-22T01:35:29Z","timestamp":1513906529000},"page":"E345-E351","source":"Crossref","is-referenced-by-count":17,"title":["Oxytocin increases the [Ca<sup>2+<\/sup>]<sub>i<\/sub>sensitivity of human  myometrium during the falling phase of phasic contractions"],"prefix":"10.1152","volume":"276","author":[{"given":"Keena","family":"McKillen","sequence":"first","affiliation":[{"name":"Department of Pharmacology, University of Cambridge, Cambridge CB2 1QJ;"},{"name":"Department of Obstetrics and Gynaecology, University of Cambridge, Rosie Hospital, Cambridge CB2 2SW; and"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Steven","family":"Thornton","sequence":"additional","affiliation":[{"name":"Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Colin W.","family":"Taylor","sequence":"additional","affiliation":[{"name":"Department of Pharmacology, University of Cambridge, Cambridge CB2 1QJ;"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"24","reference":[{"key":"B1","doi-asserted-by":"publisher","DOI":"10.1016\/0968-0004(94)90112-0"},{"key":"B2","doi-asserted-by":"publisher","DOI":"10.1111\/j.1471-0528.1967.tb03775.x"},{"key":"B3","doi-asserted-by":"publisher","DOI":"10.1126\/science.6278592"},{"key":"B4","doi-asserted-by":"publisher","DOI":"10.1016\/0002-9378(81)90270-2"},{"key":"B5","doi-asserted-by":"publisher","DOI":"10.1016\/S0002-9378(94)70214-4"},{"key":"B6","first-page":"1","volume":"16","author":"Hollingsworth M.","year":"1988","journal-title":"Med. 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