Abstract
Oxygen consumption of liver slices from male Wistar rats was determined three times a day, morning, early afternoon and evening, by means of the Warburg manometric method.
Under the lighting regimen of LD 12:12, light from 7:00 to 19:00, there was observed a circadian rhythm, with a trough at the onset of light and a peak just prior to the onset of darkness. After the inversion of the lighting regimen, i.e. light from 19:00 to 7:00, the phase of Qo2 and Qo2 (N) shifted gradually and reached eventually to 180° reversal by four weeks after the inversion of lighting.
Our results suggest that there exists a endogenous periodicity in oxygen consumption of the liver tissue, which is entrained to a light-dark cycle as Zeitgeber and consequently appears as a circadian rhythm.
