Lipid Domains in Plasma Membrances from Rat Liver

Abstract

The existence of fluid and solid lipid domains in isolated rat-liver plasma membranes was evaluated using the fluorescent fatty acids trans-parinaric and cis-parinaric acid as probe molecules for solid and Auid membrane areas, respectively. The fluorescence probe 1,6-diphenyl-l,3,5-hexatriene indicated that a phase transition was present in the liver plasma membrane between 18 "C and 30 "C. At intermediate temperatures, cis-parinaric acid, which partitioned approximately equally into fluid and soIid lipid areas, detected two lipid domains : the mole fractions of fluid and solid lipid domains at 24°C were 0.32 and 0.68 while the mole fractions of cis-parinaric acid in each domain were 0.34 and 0.66, respectively. The dissociation constant, aqueous to membrane lipid partition coefficient, and bound to free ratio for trans-parinaric acid were 7.0 0.7 pM, 4.0 & 0.6 x lo6, and 83: 17, respectively. The affinity of the membrane for cis-parinaric acid was twofold lower than for trans-parinaric acid. The trans-parinaric acid partitioned preferentially into solid lipid. K;' = 3.30, while the cis-parinaric acid partitioned equally between fluid and solid phases KJ' = 0.92. Thus, the data demonstrate the coexistence of fluid and solid domains in rat liver plasma membranes. It should be noted that the liver hepatocyte contains several different types of cell membranes. The membranes have different polarity depending on whether they are exposed to the blood circulation or to the bile. The procedure used for isolating liver plasma membrane in the present investigation largely removed the blood-front plasma membrane while purirying the bile-front area [12]. The enzymes 5'-nucleotidase and Mg-ATPase were purified 18-fold and 22-fold respectively with respect to the crude homogenate. These enzymes were assayed as described previously [14]. The Mg-ATPase was measured in the presence of ouabain. Cytochemical studies have localized Mg-ATPase to the canalicular surface [15]. The liver plasma membranes had the following lipid

Thermotropic lipid phase separations in human erythrocyte ghosts and cholesterol-enriched rat liver plasma membranes

“…These results allow us to refine an earlier model presented to account for the temperature-dependent lipid phase separation in native rat liver plasma membranes [17,20]. Above 28~ bulk lipid is proposed to be homogeneously-distributed as L. Below The high temperature break is detected by spin [20,36] and fluorescence [40] probes, DSC [30] and light scattering [11]. Since no solid or gel phase lipid (S) was detected in electron diffraction experiments for temperatures immediately below 28~ [26], we suggested that the fluidity and packing density of QCC are in between that of S and L [20].…”

Gel Domains in the Plasma Membrane of Saccharomyces cerevisiae

“…On another hand, the amplitude of the long lifetime component is proportional to the amount of the ordered domains relative to the whole membrane (16,18,22,36,37). From Figs.…”

“…The probe t-PnA presents the additional benefit of displaying a long lifetime component in its fluorescence intensity decay that is characteristic of the type of ordered domains being detected, namely gel ordered (if clearly above 30 ns) or liquid ordered (below 30 ns) domains (18 -21). This probe has been used to characterize membrane domains in different types of mammalian cells (22,23) but has never been used in yeast cells.…”

Cold Adaptation in Ectotherms: Regulation of Membrane Function and Cellular Metabolism

“…Although phase transitions and separations have been widely reported among membranes of homeotherms (Inesi et al 1973;Livingstone and Schachter 1980;Brasitus et al 1980;Schroeder 1983;Lepock et al 1983), phase transitions based upon unambiguous physical evidence have not been widely reported in multicellular ectotherms. For example, the temperature dependence of diphenylhexatriene (DPH) fluorescence polarization has failed to indicate a phase transition in brush border membranes of trout enterocytes (over a thermal range of 3-33°C; Di Constanzo et al 1983), plasma membranes (0-40°C) of the slime mold Dictyostelium discoideum (Herring et al 1980), brain synaptosomes (Cossins 1977;Cossins et al 1981) and sarcoplasmic reticulum (0-35°C) in goldfish, mitochondrial and microsomal membranes of green sunfish liver (Cossins et al 1980), vesicles of liver phospholipid from winter-adapted Chana punctatus (Dutta et al 1985), and plasma membranes of pinfish lymphocytes (Abruzzini et al 1982).…”