[Circadian rhythms in rat and mouse urinary electrolytes and nitrogen derivatives excretion (author's transl)]

The present study considers circadian rhythms of excretion of six solutes in the urine of 40 rats and 100 mice collected during eight consecutive, six-hour long periods. 1. The different chronograms evidence significant diurnal variations in water, sodium, potassium, urea, creatinine and proteins excretion of the two rodent urines. To compare easily the circadian variations in rat and mouse (with very marked differences in excretion intensities), the value of each urinary solute for each six-hour period is given as a percent of the total 24 hours excretion. 2. Daily excretion represents only 34 to 44% of the total 24 hour excretion. 3. These variations are exactly reproduced on the two consecutive days. 4. Chronogram drawings of the circadian variations of these six urinary solutes are very comparable in each rodent. 5. Moreover, these circadian variations in excretion are very similar, when compared in rat and mouse; the difference between homologous values in the two rodents is less than 2% in 2/3 of the cases.