| Abstract: | To investigate the mechanism that controls circadian rhythms in mammalian peripheral tissues, we housed mice in short days (6 h light: 18 h dark) or long days (18 h light: 6 h dark) and examined the rhythmic expression patterns of the mammalian clock genes mPer1 , mPer2 and mPer3 and a clock-controlled gene Dbp in the mouse heart. Northern blot analyses showed that peak levels of mPer1 mRNA expression in long days were about 50 % higher than those in short days. On the contrary the amplitude of the mPer2 mRNA peak in long days was about 25 % lower than that in short days. We could not find any effect of photoperiod on either the amplitude or waveform of the rhythms of mPer3 and Dbp mRNAs. Photoperiod differentially affected the expression of three mPer genes even in a peripheral tissue of mice. |
