Membranes of fat globules of cow milk contained 163 pg/lOO mg (dry weight) of glycosaminoglycans (expressed as uronic acid); 62.5% of the uronic acids corresponded to hyaluronic acid, the remaining consisted of sulfated glycosaminoglycans (chondroitin-4-(-6) sulfates, and dermatan and heparan sulfates) with different degrees of sulfation. The present report deals with the isolation and characterization of these glycoconjugates from the fat globule membrane of cow milk. METHODSThe membrane fraction was obtained from a pool of 10 liters of cow milkby churning and centrifugation [7] . Electron microscopic controls revealed a rather pure membrane preparation devoid of casein granules.volumes of chloroform-methanol (2: 1, by volume), digested for 6 h with papain [8] , treated with trichloroacetic acid (10% final concentration), neutralized with NaOH, and run through a Sephadex G-50 column (2.5 X 30 cm). The excluded material was dried, digested with ribonuclease [9] , and rechromatographed on Sephadex G-50. This crude preparation was fractionated on a DEAE-Sephadex A-25 column (0.25

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Glycosaminoglycans were isolated from plasma membranes of hepatic and renal tubule cells of guinea pig. Plasmalemma of renal tubule cells contained more total glycosaminoglycans, hyaluronic acid, chondroitin-4 sulfates and chondroitin-6 sulfates, and less dermatan sulfates and heparin sulfates than liver plasma membranes. These glycocalyx components, owing to their polyanionic properties, may have a role in the transport of water, ions, and macromolecules across the cell membrane.

Isolated tubules of the renal medulla of guinea-pig and rat contained glycosaminoglycans. 20--25% of the uronic acids corresponded to hyaluronic acid. In the guinea-pig, chondroitin and dermatan-sulfates accounted for at least 50% of the uronic acids, whereas, in the rat, heparan sulfates comprised 65--70% of them.

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