Glycosaminoglycan Content, Oxalate Self-Exchange and Protein Phosphorylation in Erythrocytes of Patients with ‘Idiopathic’ Calcium Oxalate Nephrolithiasis

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Abstract
1. This study was performed to test the hypothesis that glycosaminoglycans may play an important role in the observed abnormalities in oxalate flux seen in patients with calcium oxalate nephrolithiasis. 2. Oxalate flux rate, erythrocyte membrane glycosaminoglycan content, membrane protein phosphorylation and effect of heparan sulphate on erythrocyte oxalate flux in vitro were studied in control subjects and patients with calcium oxalate nephrolithiasis. 3 In comparison with control subjects, renal stone-formers showed a significantly higher oxalate self-exchange, a lower erythrocyte membrane glycosaminoglycan content and a higher membrane phosphorylation rate. In stone-formers, erythrocyte glycosaminoglycan content correlated inversely with the both oxalate flux rate and protein phosphorylation. In vitro, heparan sulphate promoted a significant fall in the rate of oxalate self-exchange. 4. These findings support the hypothesis that a lower erythrocyte membrane content of glycosaminoglycans enhances membrane protein phosphorylation, leading to an increased rate of transmembrane oxalate flux.