engleski

EPR spectroscopic parameters for membrane organelles from rat kidney cortex

Brush border membane, basolateral membrane and endocytotic vesicles from the mammalian proximal tubule cells are structurally heterogeneous, and are associated with different roles in kidney function. Besides having different sets of transporters, these three types of membrane organelles also differ in lipid composition. In order to examine whether these differences in lipid composition could be investigated with EPR spectroscopy with the use of spin labeled fatty-acid analogues, all three types of renal organelles were isolated from the kidney cortex of intact rats by standard procedures. Their membranes were spin labeled by lipophylic spin probe, MeFASL (10, 3) for EPR analysis. The EPR spectra were taken at various temperatures ranging from 22 to 42 °C. The spectra were analyzed by comparing experimentally observed line shapes with the lines shapes calculated according to the theoretical model developed for liquid crystals. The deduced order parameters and rotational correlation times refer to the molecular ordering and mobility, respectively, in the lipid phase of the labeled membranes. In the fitting procedure three different lipid domains were assumed. The results clearly revealed differences in the lipid ordering and rotational correlation times among all three types of membrane organelles. The ratio of the lipid domains in each type of membranes and the parameters characterizing different domains will be useful quantities in future studies of various experimental pathophysiological and toxicological entities, such as diabetes mellitus and heavy metal nephrotoxicity, that may be associated with lipid abnormalities.

brush border membrane; basolateral membrane; endocytic vesicles

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