Is renal lithium clearance altered in essential hypertension?

In order to assess whether enhanced fractional sodium reabsorption in the proximal tubule might contribute to the development of essential hypertension, we examined the relationship between arterial blood pressure and lithium clearance (CLi; used as an estimate of end-proximal fluid delivery) or fractional lithium excretion [FELi; measured using the clearances of creatinine and 51Cr ethylenediamine tetraacetic acid (EDTA) as estimates of glomerular filtration rate] in normal young males (n = 32) and in patients with essential hypertension (n = 44). In neither group was there evidence of a negative correlation between blood pressure and CLi or FELi. Mean values for CLi and FELi in a subgroup of hypertensive patients (n = 20) were almost identical to those in 20 normotensives matched for age, sex and race. These results provide no support for suggestions that a defect in proximal tubular sodium handling is an important factor in the development and/or maintenance of essential hypertension.