Renal function testing: differentiation between a nephrotoxic agent and diuretic drugs.

Preliminary studies indicate that it may be possible to differentiate the effects of a nephrotoxic substance from those of diuretic agents by the measurement of both urine and plasma osmolarity. The nephrotoxic substance, mercuric chloride, decreases urinary osmolality and increases plasma or serum osmolality. The diuretic agents, at exceedingly high dosages, may show a dose-related decrease in urine osmolality. However, serum osmolality either remains unchanged or is only slightly lowered. This difference in the serum response of animals treated with a nephrotoxin or diuretic agents may allow for the differentiation in toxicological studies.