{"title":"膜脂流动性影响离体大鼠肝细胞中5-羟硬脂酸的氮氧化物自由基衰变。","authors":"T Shima, T Nakashima, K Kashima, H Nishikawa","doi":"10.3109/10715769309056s149","DOIUrl":null,"url":null,"abstract":"<p><p>We investigated the effect of membrane fluidity on the nitroxide radical decay rate of 5-doxyl stearic acid in spin-labeled rat hepatocytes. The half-time (t1/2) for the EPR signal decay of 5-doxyl stearic acids incorporated into the membranes of isolated rat hepatocytes was 12 min (mean value). When spin-labeled hepatocytes were separated into membrane and cytosol fractions, the t1/2 of the membrane fraction was prolonged by more than 2 hrs. However, when the cytosolic fraction was added to the membrane fraction, the radical decay reaction recovered (t1/2 was 27 min). Incubation of hepatocytes with a stream of 95% O2 at 37 degrees C for 2 hrs prolonged t1/2 by 106% and was associated with a 18% decrease in water-soluble antioxidant content. When the measurement temperature was changed from 24 degrees C to 37 degrees C, t1/2 was shortened with a decrease in the order parameter (S). The t1/2 and S in hepatocytes treated with phosphatidylcholine (PC) were reduced by 14% and 0.008, respectively. Conversely, after treatment with phosphatidylethanolamine (PE), PC+cholesterol and PE+cholesterol, t1/2 and S increased by 14% and 0.014, 20% and 0.018 and 29% and 0.040, respectively. These findings suggest that the nitroxide radical decay of 5-doxyl stearic acids incorporated into hepatocyte membranes is mediated by the antioxidants in the cytosol fraction, and that the nitroxide radical decay rate is affected not only by water-soluble antioxidant content but also by the membrane lipid fluidity of the hepatocytes.</p>","PeriodicalId":12438,"journal":{"name":"Free radical research communications","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"1993-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3109/10715769309056s149","citationCount":"3","resultStr":"{\"title\":\"Membrane lipid fluidity affects the nitroxide radical decay of 5-doxyl stearic acids in isolated rat hepatocytes.\",\"authors\":\"T Shima, T Nakashima, K Kashima, H Nishikawa\",\"doi\":\"10.3109/10715769309056s149\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p><p>We investigated the effect of membrane fluidity on the nitroxide radical decay rate of 5-doxyl stearic acid in spin-labeled rat hepatocytes. The half-time (t1/2) for the EPR signal decay of 5-doxyl stearic acids incorporated into the membranes of isolated rat hepatocytes was 12 min (mean value). When spin-labeled hepatocytes were separated into membrane and cytosol fractions, the t1/2 of the membrane fraction was prolonged by more than 2 hrs. However, when the cytosolic fraction was added to the membrane fraction, the radical decay reaction recovered (t1/2 was 27 min). Incubation of hepatocytes with a stream of 95% O2 at 37 degrees C for 2 hrs prolonged t1/2 by 106% and was associated with a 18% decrease in water-soluble antioxidant content. When the measurement temperature was changed from 24 degrees C to 37 degrees C, t1/2 was shortened with a decrease in the order parameter (S). The t1/2 and S in hepatocytes treated with phosphatidylcholine (PC) were reduced by 14% and 0.008, respectively. Conversely, after treatment with phosphatidylethanolamine (PE), PC+cholesterol and PE+cholesterol, t1/2 and S increased by 14% and 0.014, 20% and 0.018 and 29% and 0.040, respectively. These findings suggest that the nitroxide radical decay of 5-doxyl stearic acids incorporated into hepatocyte membranes is mediated by the antioxidants in the cytosol fraction, and that the nitroxide radical decay rate is affected not only by water-soluble antioxidant content but also by the membrane lipid fluidity of the hepatocytes.</p>\",\"PeriodicalId\":12438,\"journal\":{\"name\":\"Free radical research communications\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":0.0000,\"publicationDate\":\"1993-01-01\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://sci-hub-pdf.com/10.3109/10715769309056s149\",\"citationCount\":\"3\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Free radical research communications\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/10.3109/10715769309056s149\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Free radical research communications","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.3109/10715769309056s149","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
Membrane lipid fluidity affects the nitroxide radical decay of 5-doxyl stearic acids in isolated rat hepatocytes.
We investigated the effect of membrane fluidity on the nitroxide radical decay rate of 5-doxyl stearic acid in spin-labeled rat hepatocytes. The half-time (t1/2) for the EPR signal decay of 5-doxyl stearic acids incorporated into the membranes of isolated rat hepatocytes was 12 min (mean value). When spin-labeled hepatocytes were separated into membrane and cytosol fractions, the t1/2 of the membrane fraction was prolonged by more than 2 hrs. However, when the cytosolic fraction was added to the membrane fraction, the radical decay reaction recovered (t1/2 was 27 min). Incubation of hepatocytes with a stream of 95% O2 at 37 degrees C for 2 hrs prolonged t1/2 by 106% and was associated with a 18% decrease in water-soluble antioxidant content. When the measurement temperature was changed from 24 degrees C to 37 degrees C, t1/2 was shortened with a decrease in the order parameter (S). The t1/2 and S in hepatocytes treated with phosphatidylcholine (PC) were reduced by 14% and 0.008, respectively. Conversely, after treatment with phosphatidylethanolamine (PE), PC+cholesterol and PE+cholesterol, t1/2 and S increased by 14% and 0.014, 20% and 0.018 and 29% and 0.040, respectively. These findings suggest that the nitroxide radical decay of 5-doxyl stearic acids incorporated into hepatocyte membranes is mediated by the antioxidants in the cytosol fraction, and that the nitroxide radical decay rate is affected not only by water-soluble antioxidant content but also by the membrane lipid fluidity of the hepatocytes.