[Circadian rhythm of metabolic rate in isolated tissue (author's transl)]

The circadian variation of oxygen uptake of isolated mouse diaphragm has been measured by means of the direct Warburg-technique in two series with sets of each 8 successive experiments. Under our experimental conditions oxygen uptake in the isolated diaphragm remains constant for 5 hours at least. The 24-hour period could therefore be completed with 8 single measurements of each 10--20 isolated diaphragms started at 3 h intervals with a overlap in experimental time of 2 h hours between each single experiment. Similar to the results concerning the spontaneous locomotive activity of the mouse (ASCHOFF 1955) we found maximum values of metabolic rate during the night, minimum values during day time and a interpolated relative maximum of oxygen uptake between 6(00)--8(00) h. Oxygen uptake after the stabilisation period of approximately 1 h seems to be determined by the time of the death of the animal.