[Circadian and seasonal rhythms of the hepatic microsomal mixed function oxidase system in 60- and 100-day-old rats]

The purpose of this work was to determine seasonal differences in circadian activity microsomal mixed-function oxidases in mature rats. The experiments were carried in four seasons (spring, summer, autumn and winter) on 60- and 100-days old Wistar males rats. The animals were bred in constant condition, illumination (12:12) i.e. 06.00-18.00 h light, 18.00-06.00 h dark and in uniform temperature (about 20 degrees C) as well as in unchanging humidity (60%). The experiments were carried in 48 hours cycle i.e. at 10.00, 14.00, 18.00, 22.00, 02.00 and 06.00. In each experimental group results are mean value from five delineation. Microsomal fraction were isolated by Dallner method. The contents of cytochrome P-450 and cytochrome b5 were determined by the method of Estabrook and Werringloer, activity of reductases: NADPH-cytochrome P-450 and NADH-cytochrome b5 (by Hodges and Leonard method) and protein content by Lowry et al. Experimental groups were compared for statistically significant differences by analysis of variance and t test. The obtained results showed differences in seasonal and circadian rhythmicity of examined parameters.