The effects of diuretics on renal clearances in pigs.

The following diuretics have been examined for their influence on renal clearances in pigs: chlorthiazidum (2 mg/kg), hydrochlor-thiazidum (0.2 and 2 mg/kg), furosemidum (0.5 mg/kg) and mer- salylum (2.5 and 10 mg/kg). The investigation comprised determinationof the clearances of inulin, endogenous creatinine, urea, PAH, sodium, potassium and chloride, before and after the administration of the diuretics. Ghlorthiazidum, hydrochlorthiazidum and mersalylum in the low dose did not affect the clearances of inulin, endogenous creatinine, urea and PAH. When furosemidum was administered, there was first a slight increase and then a decrease in those clearances. After administration of 10 mg/kg mersalylum, there was a strong decrease in the inulin, endogenous creatinine, urea and PAH clearances, and simultaneously glucose and protein could be found in the urine. All four diuretics caused a markedly increased excretion of sodium and chloride, while the excretion of potassium was only moderately increased. The effect on the excretion of sodium and chloride was of about the same order of magnitude for chlorthiazidum and hydrochlorthiazidum, though the effect of the latter was slightly more prolonged. In contrast to those two diuretics, furosemidum had a very strong but short effect. The influence of mersalylum on the excretion of sodium and chloride was somewhat stronger and more prolonged than that of the thiazides. Histological examinations of the kidneys of the pigs given 10 mg/kg mersalylum revealed pronounced tubular degeneration, particularly in the proximal tubules.