The influence of sodium and potassium supplements on the diuretic responses to frusemide administration in normal subjects.

1 Twelve normal subjects received (1) normal diet, (2) normal diet with 100 mmol supplementary sodium chloride and (3) normal diet with 96 mmol supplementary potassium chloride, each for 10 days, in a balanced cross-over study according to a Latin Square design. At the end of each study period, the subjects received 80 mg frusemide orally. Each study period was separated from the other by 10 days. 2 Changes in urinary electrolyte excretion occurred within the first four days of each dietary period then remained constant, with significant differences in urinary Na/K ratio between the dietary regimes. 3 Between-subject correlations, using the mean values over the three study periods, demonstrated significant associations between plasma uric acid and urinary Na/K ratio and between plasma prolactin and urinary potassium excretion. 4 Urinary potassium excretion and Na/K ratio following frusemide were influenced significantly by alteration of diet but there was no change in sodium excretion. 5 Between-subject correlations of pretreatment variables with diuretic response, using the mean values over the three study periods, demonstrated significant associations between both pretreatment urinary Na/K ratio and plasma uric acid and respectively the urinary potassium excretion and urinary Na/K ratio in response to frusemide. 6 While the response to frusemide was altered by short-term changes in dietary sodium and potassium, the difference was less than expected from observations in two populations with customary diets differing in similar manner.