RENAL TUBULAR FUNCTION IN CHILDREN AND ADOLESCENTS WITH GITELMANS SYNDROME, THE HYPOCALCIURIC VARIANT OF BARTTERS-SYNDROME

Renal tubular function was studied in 14 patients with Gitelman's synd rome and 14 control subjects. Apart from the biochemical hallmarks of Gitelman's syndrome, namely alkalaemia, hyperbicarbonataemia, hypokala emia, hypomagnesaemia (with increased magnesium over creatinine ratio) , increased urinary chloride over creatinine ratio, and low urinary ca lcium over creatinine, the patients were found to have hyperproteinaem ia, hypochloraemia, high total plasma calcium concentration, reduced p lasma ionized calcium concentration, and high urinary sodium excretion . A statistically significant negative linear relationship between pla sma magnesium concentration and magnesium excretion corrected for glom erular filtration was observed in patients. The fractional calcium cle arance and the urinary excretion of calcium corrected for glomerular f iltration was significantly decreased in patients. In patients the uri nary osmolality after overnight water deprivation ranged from 526 to 1 067 mmol/kg. Glucosuria and aminoaciduria were similar in patients and controls. The results of the study demonstrate the renal origin of hy pomagnesaemia and hypocalciuria in Gitelman's syndrome. The failure to demonstrate hyperaminoaciduria, hyperglucosuria, hyperphosphaturia, h yperuricosuria, and severely impaired urinary concentrating ability pr ovide evidence for a defect residing in the distal convoluted tubule.