Cholesterol affects physical properties and (Na+,K+)-ATPase in basolateral membranes of renal and intestinal epithelia from thermally acclimated rainbow trout |
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Authors: | Elizabeth L Crockett Jeffrey R Hazel |
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Institution: | (1) Department of Biological Sciences, Ohio University, Athens, OH 45701 USA, Tel.: +1-614/593-9470, Fax: +1-614/593-0300, e-mail: crockett@mail.ovcom.ohiou.edu, US;(2) Department of Zoology, Arizona State University, Tempe, AZ 85287 USA, US |
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Abstract: | Previous work has shown that cholesterol levels are modulated in plasma membranes from some but not all tissues of poikilotherms
over the course of temperature change. To gain a better understanding of tissue and membrane domain-specific cholesterol function
during thermal adaptation we examined effects of cholesterol on membrane physical properties and (Na+,K+)-ATPase in native and cholesterol-enriched basolateral membranes from kidney and intestine of thermally acclimated trout
(Oncorhynchus mykiss). Membrane order (as indicated by fluorescence depolarization studies) is increased, whereas its thermal sensitivity is decreased
by elevated cholesterol levels in mem branes with relatively low endogenous amounts of cholesterol (intestinal membranes and
renal membranes from cold-acclimated fish). Thermal sensitivities of membrane order in kidney are 1.5-fold higher in native
compared with cholesterol-enriched basolateral membranes. For renal plasma membranes, (Na+,K+)- ATPase activity is lowest near the transition between native and surpraphysiological cholesterol levels. Endogenous cholesterol
levels (relative to phospholipid contents) in intestinal basolateral membranes from cold-acclimated fish vary more than 1.5-fold;
membranes with cholesterol/phospholipid molar ratios of 0.3 have activities of (Na+,K+)-ATPase that are twofold lower than native membranes having a ratio of 0.2. These results suggests that maintenance of cholesterol
levels in intestinal basolateral membranes during thermal acclimation may ensure sufficient activity of (Na+,K+)-ATPase. Membrane function in kidney, with its high native cholesterol content, is less likely to be affected by temperature
change.
Accepted: 21 January 1997 |
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Keywords: | Cholesterol (Na+ K+)-ATPase Membrane order Plasma membrane Temperature adaptation |
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