{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,3]],"date-time":"2025-11-03T13:34:13Z","timestamp":1762176853035},"reference-count":0,"publisher":"Portland Press Ltd.","issue":"3","content-domain":{"domain":["portlandpress.com"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[1990,11,1]]},"abstract":"<jats:p>Sheep anterior-pituitary cells permeabilized with Staphylococcus aureus alpha-toxin were used to investigate the role of cyclic AMP (cAMP) in exocytosis of luteinizing hormone (lutropin, LH) under conditions where the intracellular free Ca2+ concentration ([Ca2+]free) is clamped by Ca2+ buffers. At resting [Ca2+]free (pCa 7), cAMP rapidly stimulated LH exocytosis (within 5 min) and continued to stimulate exocytosis for at least 30 min. When cAMP breakdown was inhibited by 3-isobutyl-1-methylxanthine (IBMX), the concentration giving half-maximal response (EC50) for cAMP-stimulated exocytosis was 10 microM. cAMP-stimulated exocytosis required millimolar concentrations of MgATP, as has been found with Ca2(+)- and phorbol-ester-stimulated LH exocytosis. cAMP caused a modest enhancement of Ca2(+)-stimulated LH exocytosis by decreasing in the EC50 for Ca2+ from pCa 5.6 to pCa 5.9, but had little effect on the maximal LH response to Ca2+. Activation of protein kinase C (PKC) with phorbol 12-myristate 13-acetate (PMA) dramatically enhanced cAMP-stimulated LH exocytosis by both increasing the maximal effect 5-7-fold and decreasing the EC50 for cAMP to 3 microM. This synergism between cAMP and PMA was further augmented by increasing the [Ca2+]free. Gonadotropin-releasing hormone (gonadoliberin, GnRH) stimulated cAMP production in intact pituitary cells. Since GnRH stimulation is reported to activate PKC and increase the intracellular [Ca2+]free, our results suggest that a synergistic interaction of the cAMP, PKC and Ca2+ second-messenger systems is of importance in the mechanism of GnRH-stimulated LH exocytosis.<\/jats:p>","DOI":"10.1042\/bj2710635","type":"journal-article","created":{"date-parts":[[2015,8,10]],"date-time":"2015-08-10T21:18:17Z","timestamp":1439241497000},"page":"635-639","update-policy":"http:\/\/dx.doi.org\/10.1042\/crossmark_policy","source":"Crossref","is-referenced-by-count":30,"title":["Cyclic AMP stimulates luteinizing-hormone (lutropin) exocytosis in permeabilized sheep anterior-pituitary cells. Synergism with protein kinase C and calcium"],"prefix":"10.1042","volume":"271","author":[{"given":"M B","family":"Macrae","sequence":"first","affiliation":[{"name":"Medical Research Council Regulatory Peptides Research Unit, Department of Chemical Pathology, University of Cape Town Medical School, Observatory 7925, Cape Town, South Africa."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"J S","family":"Davidson","sequence":"additional","affiliation":[{"name":"Medical Research Council Regulatory Peptides Research Unit, Department of Chemical Pathology, University of Cape Town Medical School, Observatory 7925, Cape Town, South Africa."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"R P","family":"Millar","sequence":"additional","affiliation":[{"name":"Medical Research Council Regulatory Peptides Research Unit, Department of Chemical Pathology, University of Cape Town Medical School, Observatory 7925, Cape Town, South Africa."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"P A","family":"van der Merwe","sequence":"additional","affiliation":[{"name":"Medical Research Council Regulatory Peptides Research Unit, Department of Chemical Pathology, University of Cape Town Medical School, Observatory 7925, Cape Town, South Africa."}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"288","container-title":["Biochemical Journal"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/portlandpress.com\/biochemj\/article-pdf\/271\/3\/635\/602092\/bj2710635.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/portlandpress.com\/biochemj\/article-pdf\/271\/3\/635\/602092\/bj2710635.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2021,11,25]],"date-time":"2021-11-25T18:44:11Z","timestamp":1637865851000},"score":1,"resource":{"primary":{"URL":"https:\/\/portlandpress.com\/biochemj\/article\/271\/3\/635\/26493\/Cyclic-AMP-stimulates-luteinizing-hormone-lutropin"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1990,11,1]]},"references-count":0,"journal-issue":{"issue":"3","published-print":{"date-parts":[[1990,11,1]]}},"URL":"https:\/\/doi.org\/10.1042\/bj2710635","relation":{},"ISSN":["0264-6021","1470-8728"],"issn-type":[{"value":"0264-6021","type":"print"},{"value":"1470-8728","type":"electronic"}],"subject":[],"published":{"date-parts":[[1990,11,1]]}}}