{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,17]],"date-time":"2026-08-17T22:09:27Z","timestamp":1787004567224,"version":"build-2736575974"},"reference-count":0,"publisher":"Portland Press Ltd.","issue":"2","content-domain":{"domain":["portlandpress.com"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[1989,7,15]]},"abstract":"<jats:p>Lung contains both Mg2+-dependent and Mg2+-independent phosphatidate phosphohydrolase activities. Addition of Triton X-100 (0.5%) or chlorpromazine (1 mM) leads to a marked increase in the total phosphatidate phosphohydrolase activity in rat lung microsomes (microsomal fractions), but a decrease in the Mg2+-dependent activity. These observations suggest that the Mg2+-independent activity is stimulated, whereas the Mg2+-dependent activity is inhibited. However, the possibility exists that Triton X-100 could stimulate the Mg2+-dependent enzymic activity in an Mg2+-independent manner. In addition, the positively charged amphiphilic drug could be replacing the enzyme's requirement for Mg2+. These two possibilities were examined by using subcellular fractions in which the Mg2+-dependent phosphatidate phosphohydrolase had been abolished by heat treatment at 55 degrees C for 15 min. Heat treatment does not affect the microsomal Mg2+-independent phosphohydrolase to any great extent. Since the 6-8-fold stimulations due to Triton X-100 and chlorpromazine are retained after heat treatment of this fraction, the Mg2+-independent activity must be involved. Addition of Triton X-100 and chlorpromazine to cytosol virtually abolishes the Mg2+-dependent phosphatidate phosphohydrolase activity and decreases the Mg2+-independent activity by half. Heat treatment also abolishes the Mg2+-dependent activity and decreases the Mg2+-independent activity by over half. The Mg2+-independent phosphatidate phosphohydrolase activity remaining after heat treatment was not affected by Triton X-100 or chlorpromazine. These studies demonstrate that Triton X-100 and chlorpromazine specifically stimulate the heat-stable Mg2+-independent phosphatidate phosphohydrolase activity in rat lung microsomes. In contrast, the heat-labile Mg2+-independent phosphatidate phosphohydrolase activities in cytosol are inhibited by these reagents. Triton X-100 and chlorpromazine inhibit the Mg2+-dependent phosphatidate phosphohydrolase activities in both rat lung microsomes and cytosol. These results are consistent with the view that a single Mg2+-dependent phosphatidate phosphohydrolase present in both microsomes and cytosol is specifically involved in glycerolipid metabolism.<\/jats:p>","DOI":"10.1042\/bj2610673","type":"journal-article","created":{"date-parts":[[2015,8,10]],"date-time":"2015-08-10T17:13:56Z","timestamp":1439226836000},"page":"673-678","update-policy":"https:\/\/doi.org\/10.1042\/crossmark_policy","source":"Crossref","is-referenced-by-count":14,"title":["The effects of Triton X-100 and chlorpromazine on the Mg2+-dependent and Mg2+-independent phosphatidate phosphohydrolase activities of rat lung"],"prefix":"10.1042","volume":"261","author":[{"given":"P A","family":"Walton","sequence":"first","affiliation":[{"name":"Departments of Biochemistry and Obstetrics & Gynaecology, University of Western Ontario, London, Ontario, Canada N6A 5A5."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"F","family":"Possmayer","sequence":"additional","affiliation":[{"name":"Departments of Biochemistry and Obstetrics & Gynaecology, University of Western Ontario, London, Ontario, Canada N6A 5A5."}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"288","container-title":["Biochemical Journal"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/portlandpress.com\/biochemj\/article-pdf\/261\/2\/673\/597328\/bj2610673.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/portlandpress.com\/biochemj\/article-pdf\/261\/2\/673\/597328\/bj2610673.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2021,11,25]],"date-time":"2021-11-25T13:18:01Z","timestamp":1637846281000},"score":1,"resource":{"primary":{"URL":"https:\/\/portlandpress.com\/biochemj\/article\/261\/2\/673\/25234\/The-effects-of-Triton-X-100-and-chlorpromazine-on"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1989,7,15]]},"references-count":0,"journal-issue":{"issue":"2","published-print":{"date-parts":[[1989,7,15]]}},"URL":"https:\/\/doi.org\/10.1042\/bj2610673","relation":{},"ISSN":["0264-6021","1470-8728"],"issn-type":[{"value":"0264-6021","type":"print"},{"value":"1470-8728","type":"electronic"}],"subject":[],"published":{"date-parts":[[1989,7,15]]}}}