1) The amounts of individual mucopolysaccharides in the new born rat skin have been estimated and their specific rates of labelling assessed in vitro. Total and percentage amounts of these polymers agree satisfactorily with previously published data. 2) Relative rates of labelling from [U14C]-glucose have been estimated by combining column chromatography separation and electrophoresis on cellulose acetate strips. Specific radioactivities have been measured either with respect to the total uronic acid content of the fractions or with respect to their quantitative staining with Alcian Blue. The two methods agreed satisfactorily. 3) Average biosynthetic rates almost identical for hyaluronic acid and the total sulfated mucopolysaccharides. However, within the latter fraction, heparin + heparan sulfate incorporate [U14C]-glucose about 4 to 5 times more rapidly than the chondroitin sulfates. This result could not be expected from previous data obtained in vivo and is discussed with reference to a possible heterogeneity of the cell material whence the various mucopolysaccharides originate. 4) In the presence of puromycin, labelling of the sulfated mucopolysaccharides stops almost immediately, indicating a stringent requirement for protein primers. Biosynthesis of hyaluronic acid is affected only after preincubation of tissue with puromycin (one hour) and subsequent incubation of two hours with [U14C]-glucose.

Animals↗

PubMedDate not supplied

Biosynthesis of acid mucopolysaccharides by the surviving new born rat skin. II. - Specific labelling of individual monosaccharides from (U14C)-glucose. Metabolic origin of L-iduronic acid.

1)Individual monosaccharides (uronic acids and aminosugars) have been purified following specific hydrolysis of the mucopolysaccharides from new born rat skin (hyaluronic acid, heparin + heparan sulfate, chondroitin sulfate A, B and C), after incubation with [U14C]-glucose under various conditions and for varying incubation periods. The yields and the specificity of the methods used for hydrolysis are discussed. 2) Monosaccharides from hyaluronic acid and the sulfated mucopolysaccharide fraction are labelled at an approximately equal rate. In addition, high rates of labelling of glucosamine isolated from the sulfated fractions confirms the preferential labelling of (heparin + heparan sulfate) demonstrated with the sulfated polymers. 3) In all fractions, aminosugars are considerably less labelled than the corresponding uronic acids, which suggests the existence of endogeneous diluting precursor pools for the former monosaccharides. 4) No drift of radioactivity from D-glucuronate to L-iduronate could be demonstrated in sulfated mucopolysaccharides after inhibition of their biosynthesis by puromycin or diluting the labelled precursor pools. Hence it has not been possible to substantiate on the surviving tissue the C5 epimerization at the polymer level, as previously demonstrated by other authors with subcellular fractions of various origin.

Animals↗

PubMedDate not supplied

[Remarks on the mechanism of action of insulin].

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Cell Membrane↗