{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,9]],"date-time":"2026-07-09T00:17:23Z","timestamp":1783556243925,"version":"3.55.0"},"reference-count":0,"publisher":"Bioscientifica","issue":"2","content-domain":{"domain":["journals.bioscientifica.com"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[1996,2,1]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>The performance of existing immunoassays and bioassays for activins is compromised by the presence of activin-binding proteins such as follistatin and \u03b12 macroglobulin (\u03b12M) in biological fluids. To overcome this problem we have developed a novel two-site enzyme immunoassay procedure for activin-A which incorporates an analyte denaturation and oxidation step. The optimized assay is sensitive (detection limit \u223c10 pg\/well), precise (mean within- and between-plate coefficients of variation 4\u00b79 and 9\u00b71% respectively) and accurate (activin-A recovery values of 102 \u00b1 3 and 96 \u00b1 5% for bovine follicular fluid (FF) and human serum respectively). In specificity tests, high concentrations of follistatin (500 ng\/ml) and \u03b12M (100 \u03bcg\/ml) did not interfere with the response signal to activin-A. In addition, no significant cross-reactivity was observed with a range of related molecules including inhibin-A, inhibin-B, activin-B (all &amp;lt;0\u00b75%), bovine pro-\u03b1C and follistatin (both &amp;lt;0\u00b71%). Response curves parallel to the activin-A standard curve were obtained for a variety of test samples including bovine, human, ovine and porcine FF, human sera and conditioned medium from cultured bovine and human granulosa cells. Fractionation of bovine FF by SDS-PAGE confirmed assay specificity since only one peak of activin-A immunoreactivity was detected (Mr \u223c25 k) in eluted gel slices. However, gel-permeation chromatography showed that under physiological conditions all of the detectable activin-A in bovine FF eluted with apparent Mr values of &amp;gt;700 and 60\u2013200 k reflecting its association with binding protein(s). Analysis of bovine FF samples (n=76) from morphologically dominant follicles during the luteal phase showed that activin-A levels were positively correlated with inhibin-A (r=+0\u00b754; P&amp;lt;0\u00b7001) and total \u03b2 subunit immunoreactivity (r=+0\u00b732; P&amp;lt;0\u00b7005) but not with total \u03b1 subunit immunoreactivity (r= \u22120\u00b709). Classification of these follicles according to oestrogenic status showed that activin-A, inhibin-A and total \u03b2 subunit levels were highest in oestrogen-inactive follicles (P&amp;lt;0\u00b701) whereas total \u03b1 subunit levels were lowest in these follicles (P&amp;lt;0\u00b7001). Activin-A levels were measurable in all human serum samples analysed, ranging from 128 pg\/ml during the normal menstrual cycle, 210 pg\/ml in women undergoing ovarian hyperstimulation and \u223c 500 pg\/ml in postmenopausal women to over 4000 pg\/ml during pregnancy.<\/jats:p>\n                  <jats:p>In conclusion, the present assay provides a reliable method for quantitating total (i.e. bound+free) activin-A concentrations in a variety of biological samples and should prove useful for further in vivo and in vitro studies in a range of species including man.<\/jats:p>\n                  <jats:p>Journal of Endocrinology (1996) 148, 267\u2013279<\/jats:p>","DOI":"10.1677\/joe.0.1480267","type":"journal-article","created":{"date-parts":[[2004,12,2]],"date-time":"2004-12-02T18:29:37Z","timestamp":1102012177000},"page":"267-279","update-policy":"https:\/\/doi.org\/10.1530\/crossmarkpolicy-5","source":"Crossref","is-referenced-by-count":188,"title":["Development and application of a two-site enzyme immunoassay for the determination of 'total' activin-A concentrations in serum and follicular fluid"],"prefix":"10.1530","volume":"148","author":[{"given":"P G","family":"Knight","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"S","family":"Muttukrishna","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"N P","family":"Groome","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"416","container-title":["Journal of Endocrinology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/joe.bioscientifica.com\/view\/journals\/joe\/148\/2\/joe_148_2_011.xml","content-type":"text\/html","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/journals.bioscientifica.com\/joe\/article-pdf\/148\/2\/267\/104422\/joe_148_2_011.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/journals.bioscientifica.com\/joe\/article-pdf\/148\/2\/267\/104422\/joe_148_2_011.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,7,8]],"date-time":"2026-07-08T13:00:57Z","timestamp":1783515657000},"score":1,"resource":{"primary":{"URL":"https:\/\/journals.bioscientifica.com\/joe\/article\/148\/2\/267\/18450\/Development-and-application-of-a-two-site-enzyme"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1996,2,1]]},"references-count":0,"journal-issue":{"issue":"2","published-print":{"date-parts":[[1996,2,1]]}},"URL":"https:\/\/doi.org\/10.1677\/joe.0.1480267","relation":{},"ISSN":["1479-6805","0022-0795"],"issn-type":[{"value":"1479-6805","type":"electronic"},{"value":"0022-0795","type":"print"}],"subject":[],"published":{"date-parts":[[1996,2,1]]}}}