[Circadian rhythmicity of urea concentration in the liver and blood serum of cockerels].

The circadian rhythmicity of urea concentration was studied in 70 12-day-old cockerels (the Primant commercial hybrid). Urea in the liver homogenate supernatant and in the blood serum was determined by means of diacetylmonoxim (Homolka, 1971). The cockerels were killed in four-hour intervals. Urea concentration in the liver reached its peak at 15.30 o'clock (123.36 +/- 6.32 in conversion to wet tissue or 0.308 +/- 0.01 mg of nitrogen per 100 mg). The circadian rhythmicity of uremia generally coincided with the rhythmicity of urea in the liver.