Studies on the structure of the rabbit kidney brush border

The effects of salts and non-ionic detergents on renal brush borders have been studied. 2 M sodium chloride, iodide or thiocyanate dissociated up to 40% of the protein from the brush borders, destroying the core filaments and resulting in the formation of membrane vesicles; EDTA had a similar effect on structure but released little protein. Triton X-100 and Nonidet P-40 extracted up to 60% of the protein including the major membrane glycoproteins and the enzymes trehalase, maltase and aminopeptidase (microsomal). Triton exhibited a selective effect on lipids removing phosphatidylserine, phosphatidylethanolamine and sphingomyelin but not the bulk of the phosphatidylcholine or cholesterol. The residual structures after Triton extraction comprised the core filaments associated with vesicles of lipid containing alkaline phosphatase and several other proteins. Treatment of these core-vesicle complexes with 2 M sodium chloride dissociated the filaments, releasing the vesicles which could be recovered as a pellicle on centrifugation. It is suggested that the proteins found in the vesicles might serve to interconnect the core filaments with the lipid bilayer.