1. It has been proposed that the enhanced erythrocyte Na+/Li+ countertransport observed in many patients with essential hypertension could be a marker of abnormal renal proximal tubular function. We thus investigated the relationship of blood pressure and Na+/Li+ countertransport to an index of proximal tubular function such as renal Li+ clearance. 2. The study was carried out in a sample of 299 untreated male subjects (aged 21-59 years) randomly selected from a population at work. Na+/Li+ countertransport was measured in a representative sub-group of 176 men. 3. We did not detect statistically significant correlation of either blood pressure or Na+/Li+ countertransport (V(max.)) with fractional excretion of Li+, while confirming the existence of a significant continuous association of blood pressure and body mass index with Na+/Li+ countertransport (P <0.01). 4. A sub-sample of 57 participants belonging to the lowest or the highest quintiles of Na+/Li+ countertransport distribution repeated the Li+ clearance study after moderate Na+ restriction. 5. Although fractional excretions of Na+ and Li+ were reduced on the low Na+ diet (both P <0.001), they did not differ significantly between groups. 6. Our results are at variance with the findings of a recent case-control study in a young age group and suggest that further studies are necessary before a conclusion can be drawn as to the suitability of Na+/Li+ countertransport as a marker of Na+ reabsorption in the renal proximal tubule.
|Number of pages||6|
|Publication status||Published - 1989|
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