{"doi":"10.1677/joe.0.1220351","title":"Ovine placental steroid 17α-hydroxylase/C-17,20-lyase, aromatase and sulphatase in dexamethasone-induced and natural parturition","abstract":"<jats:title>ABSTRACT</jats:title>\n        <jats:p>Parturition in the sheep is preceded by an abrupt alteration in placental steroid metabolism causing a shift from progesterone to oestrogen production. This change is believed to be a consequence of the prepartum rise in cortisol in the fetal circulation and involves increases in activities of the enzymes steroid 17α-hydroxylase (cytochrome P-450<jats:sub>17α</jats:sub>), steroid C-17,20-lyase, and possibly aromatase and steroid sulphatase. The activity levels have been determined of steroid 17α-hydroxylase, aromatase and steroid sulphatase in placental microsomes in late pregnancy, dexamethasone-induced labour and in natural labour at term. Over the gestational period of 118-140 days, basal levels of placental aromatase were relatively constant (mean value (±<jats:sc>s.e.m.</jats:sc>) of 5·6 ± 0·5 pmol/min per mg microsomal protein (<jats:italic>n</jats:italic> = 10)). Pregnenolone and progesterone 17α-hydroxylase activities were undetectable (&lt; 0·5 pmol/min per mg microsomal protein (<jats:italic>n</jats:italic> = 7)). In six animals in labour induced with infusion of dexamethasone into the fetus, placental aromatase activity increased to a value of 14·0± 1·0 pmol/min per mg protein; placental pregnenolone 17α-hydroxylase, measured in four of the animals, also increased to 453 ± 77 pmol/min per mg microsomal protein. In five animals in natural spontaneous labour with vaginal delivery, aromatase activity was 26·7 ± 5·2 pmol/min per mg microsomal protein and pregnenolone 17α-hydroxylase activity was 141 ±14 pmol/min per mg microsomal protein. Steroid sulphatase activity was barely detectable (&lt; 1·5 pmol/min per mg microsomal protein) during late pregnancy, dexamethasoneinduced labour or natural parturition. Immunoblotting of placental microsomal preparations with a specific antibody to cytochrome P-450 <jats:sub>17α</jats:sub> indicated that the glucocorticoid-induced activity of steroid 17α-hydroxylase was associated with an increased content of cytochrome P-450<jats:sub>17α</jats:sub>. The cotyledon can then convert pregnenolone to dehydroepiandrosterone and thereby generate aromatizable C<jats:sub>19</jats:sub> steroids for the aromatase system to facilitate oestrogen synthesis. Importantly, the ovine placental steroid 17α-hydroxylase inefficiently metabolizes 17α-hydroxyprogesterone to androstenedione and thus progesterone is not a principal precursor of oestrogen. The data are consistent with a mechanism of glucocorticoid action in natural ovine parturition to increase cytochrome P-450<jats:sub>17α</jats:sub> synthesis either by stabilizing the mRNA for cytochrome P-450<jats:sub>17α</jats:sub> or else acting as a stimulus to transcription of the steroid 17α-hydroxylase gene.</jats:p>\n        <jats:p><jats:italic>Journal of Endocrinology</jats:italic> (1989) <jats:bold>122,</jats:bold> 351–359</jats:p>","journal":"Journal of Endocrinology","year":1989,"id":36973,"datarank":4.431965529045577,"base_score":4.418840607796598,"endowment":4.418840607796598,"self_citation_contribution":0.6628260911694899,"citation_network_contribution":3.769139437876087,"self_endowment_contribution":0.6628260911694899,"citer_contribution":3.769139437876087,"corpus_percentile":null,"corpus_rank":null,"citation_count":82,"citer_count":79,"citers_with_citation_signal":75,"citers_with_endowment":75,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":null,"is_data_producer":false,"deposit_databanks":null,"is_oa":false,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":null,"fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":186204,"name":"J. T. France","orcid":null,"position":1,"is_corresponding":false},{"id":186205,"name":"R. R. Magness","orcid":null,"position":2,"is_corresponding":false},{"id":186206,"name":"B. A. Murry","orcid":null,"position":3,"is_corresponding":false},{"id":186207,"name":"C. R. Rosenfeld","orcid":null,"position":4,"is_corresponding":false},{"id":186203,"name":"J. I. Mason","orcid":null,"position":0,"is_corresponding":false}],"reference_count":0,"raw_metadata":{"has_enrichment":true,"base_score":4.418840607796598,"endowment":4.418840607796598,"datacite_reuse_total":0,"file_count":0,"downloads":0,"views":0,"has_version_chain":false,"is_dataset":false,"is_oa":false,"pmid":"2788698","pmcid":null,"openalex_id":"https://openalex.org/W1987039281","authors":[],"funders":[{"funder_name":"NICHD NIH HHS","grant_id":"HD-08783","title":null},{"funder_name":"NICHD NIH HHS","grant_id":"HD-11149","title":null},{"funder_name":"NCI NIH HHS","grant_id":"CA-30253","title":null}],"total_grants":3,"fwci":3.9499,"citation_percentile":0.93205858,"influential_citations":4,"citation_trend":[{"year":2012,"count":3},{"year":2014,"count":3},{"year":2015,"count":1},{"year":2016,"count":3},{"year":2017,"count":3},{"year":2018,"count":2},{"year":2019,"count":1},{"year":2020,"count":1},{"year":2021,"count":2},{"year":2022,"count":1},{"year":2023,"count":1},{"year":2025,"count":1}],"oa_status":"closed","license":null,"oa_locations":[{"url":"https://joe.bioscientifica.com/view/journals/joe/122/1/joe_122_1_040.xml","host_type":"publisher"},{"url":"https://joe.bioscientifica.com/downloadpdf/journals/joe/122/1/joe_122_1_040.xml","host_type":"publisher"},{"url":"https://doi.org/10.1677/joe.0.1220351","host_type":"journal"},{"url":"https://pubmed.ncbi.nlm.nih.gov/2788698","host_type":"repository"}],"fields_of_study":["Reproductive Physiology in Livestock","Estrogen and related hormone effects","Biology","Medicine","Aldehyde-Lyases","Animals","Aromatase","Arylsulfatases","Cytochrome P-450 Enzyme System","Dexamethasone","Female","Labor, Obstetric","Microsomes","Placenta","Pregnancy","Sheep","Steroid 17-alpha-Hydroxylase","Steroid Hydroxylases","Steryl-Sulfatase"],"mesh_terms":["Aldehyde-Lyases","Animals","Aromatase","Arylsulfatases","Cytochrome P-450 Enzyme System","Dexamethasone","Female","Labor, Obstetric","Microsomes","Placenta","Pregnancy","Sheep","Steroid Hydroxylases","Steroid 17-alpha-Hydroxylase","Steryl-Sulfatase"],"keywords":["Pregnenolone","Internal medicine","Endocrinology","Aromatase","Steroid","Microsome","Biology","CYP17A1","Placenta","Chemistry","Fetus","Enzyme","Pregnancy","Biochemistry","Medicine","Hormone"],"sdg_mappings":[{"sdg_number":0,"sdg_label":"Decent work and economic growth"}],"linked_datasets":[],"clinical_trials":[],"software_tools":[],"database_accessions":[],"source":"live","citation_network_status":"fetched"},"created_at":"2026-06-10T18:00:05.635011Z","pmid":null,"pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}