{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,7]],"date-time":"2026-01-07T20:25:57Z","timestamp":1767817557450,"version":"3.49.0"},"reference-count":0,"publisher":"Oxford University Press (OUP)","issue":"1","license":[{"start":{"date-parts":[[1993,9,1]],"date-time":"1993-09-01T00:00:00Z","timestamp":746841600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/academic.oup.com\/pages\/standard-publication-reuse-rights"}],"content-domain":{"domain":["reproduction-online.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[1993,9,1]]},"abstract":"<jats:p>Immunoreactive \u03b2-endorphin (ir-BEND) and GnRH (ir-GnRH) have been identified in the pig uterus. The study reported here examined (i) possible biochemical differences between ir-BEND and ir-GnRH present in pig uterine fluids and standard synthetic peptides, and (ii) the secretory profiles of uterine ir-BEND and ir-GnRH during the oestrous cycle and early pregnancy for two breeds of pig, Large White and the highly prolific Chinese Meishan. Reverse phase (RP)-HPLC analysis of concentrated uterine fluids indicated that the majority of ir-BEND eluted with a hydrophobicity similar to that of synthetic BEND 1\u201331 (BEND) and \u03b1-N-acetylated BEND 1\u201331 (Nac-BEND), with a ratio of BEND to Nac-BEND of approximately 1.8:1. The RP-HPLC profiles of ir-GnRH demonstrated a major peak coeluting with synthetic GnRH, along with a minor peak eluting at the void volume. Total content of ir-BEND (pg per uterus) was affected by the interaction of breed with day (P &amp;lt; 0.001), but was independent of reproductive status. In Large White gilts, uterine fluid content of ir-BEND was higher (P &amp;lt; 0.05) on days 10 and 11 than on days 8, 12 and 14; however, in Meishan gilts, ir-BEND decreased from day 8 to days 10 and 11, and remained low on days 12 and 14. Compared to Meishan gilts, Large White gilts had higher ir-BEND concentrations on day 10 (P &amp;lt; 0.01), day 11 (P &amp;lt; 0.0001), day 12 (P &amp;lt; 0.01) and day 14 (P &amp;lt; 0.02). Similar patterns were detected when ir-BEND in uterine fluid was expressed as pg mg\u22121 protein. Differences in total ir-GnRH content of uterine fluid were influenced by the interaction of breed, status and day (P &amp;lt; 0.02). For Large White gilts, total ir-GnRH content was similar on days 8, 10, 11 and 12 between cyclic and pregnant gilts, but increased markedly (P &amp;lt; 0.0001) on day 14 of pregnancy. In pregnant Meishan gilts, total ir-GnRH content was increased on days 8, 12 and 14, compared with cyclic Meishan gilts on the same days. However, concentrations of ir-GnRH in uterine fluid (pg mg\u22121 protein) depended only upon the interaction of status and day (P &amp;lt; 0.03). These results suggest that ir-BEND and ir-GnRH in uterine fluids possess biochemical similarities to their respective synthetic peptides. In addition, the uterine secretory profile of ir-BEND is different in Large White and Meishan pigs but the significance of this difference is unclear. The marked increase in ir-GnRH in uterine fluids between days 12 and 14 of early pregnancy suggests that uterine ir-GnRH may play a role in early pregnancy.<\/jats:p>","DOI":"10.1530\/jrf.0.0990253","type":"journal-article","created":{"date-parts":[[2004,3,20]],"date-time":"2004-03-20T01:55:52Z","timestamp":1079747752000},"page":"253-258","update-policy":"https:\/\/doi.org\/10.1530\/rep\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":4,"title":["Secretion of immunoreactive \u03b2-endorphin and GnRH by the pig uterus: effects of reproductive status and breed"],"prefix":"10.1093","volume":"99","author":[{"given":"W. I.","family":"Li","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"S.","family":"Jiao","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"C. L.","family":"Chen","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"F. W.","family":"Bazer","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"286","published-online":{"date-parts":[[1993,9,1]]},"container-title":["Reproduction"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/academic.oup.com\/reproduction\/article-pdf\/99\/1\/253\/64815877\/jrf_99_1_036.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/academic.oup.com\/reproduction\/article-pdf\/99\/1\/253\/64815877\/jrf_99_1_036.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,1,7]],"date-time":"2026-01-07T19:08:50Z","timestamp":1767812930000},"score":1,"resource":{"primary":{"URL":"https:\/\/academic.oup.com\/reproduction\/article\/99\/1\/253\/8278181"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1993,9,1]]},"references-count":0,"journal-issue":{"issue":"1","published-print":{"date-parts":[[1993,9,1]]}},"URL":"https:\/\/doi.org\/10.1530\/jrf.0.0990253","relation":{},"ISSN":["1470-1626","1741-7899"],"issn-type":[{"value":"1470-1626","type":"print"},{"value":"1741-7899","type":"electronic"}],"subject":[],"published-other":{"date-parts":[[1993,9,1]]},"published":{"date-parts":[[1993,9,1]]}}}