Circadian rhythms in the urinary excretion of metals and organic substances in "healthy" men.

Circadian rhythms in the urinary excretion of metals and organic substances were examined in ten "healthy" men under conditions of water loading and restriction. Four characteristic rhythms were observed: (1) decreased excretion during the night for lead and urinary flow rate; (2) decreased excretion of hippuric acid, delta-aminolevulinic acid, coproporphyrin, creatinine, and total urinary solutes during the night and morning hours; (3) increased excretion of mercury and zinc during the morning hours; and (4) no significant variation for copper. Excretion of lead, hippuric acid, delta-aminolevulinic acid, and total urinary solutes was significantly correlated with urinary flow rate and creatinine excretion, which suggested that their circadian rhythms were the consequence of reduced glomerular filtration and increased reabsorption by the distal tubule and collecting duct during the night and morning hours. Similarly, it was suggested that the mercury and zinc rhythms resulted partly from increased reabsorption during the night hours; the coproporphyrin rhythm reflected reduced glomerular filtration of coproporphyrinogen during the night and morning hours.