DECREASE IN THE TIME-DEPENDENT DIFFERENCE IN URINARY-EXCRETION OF FUROSEMIDE WITH AGE

The influence of age on the time-dependent difference in urinary excre tion of furosemide, a loop diuretic agent, was examined in this longit udinal study. Male Wistar rats were maintained under conditions of lig ht from 07:00 to 19:00 h and dark from 19:00 to 07:00 h. Furosemide (3 0 mg/kg) was given orally at 12:00 h (day trial) or 00:00 h (night tri al) to rats at 3 months of age, and urine was collected for 8 h after dosage. Thereafter, the identical protocol was repeated using the same animals at 6, 9, 12, 15, 18, and 21 months of age. The urinary excret ion of furosemide was significantly greater in the day than in the nig ht trial at 3 months of age. Such a time-dependent difference was obse rved for up to 15 months, but disappeared at 18 and 21 months of age. The time-dependent difference in urinary excretion of furosemide (day trial - night trial) decreased gradually throughout the observation pe riod of the study. These results suggest that the time-dependent diffe rence in the urinary excretion of furosemide diminishes during the agi ng process and disappears by 18 months of age in male Wistar rats.