Abstract
Recently, expression levels of clock genes is found to change periodically in parallel with diurnal cycle in various peripheral tissue. To study the diurnal difference in radiation effect in small intestinal mucosa, quantitative examination in the expression of the clock genes and DNA damage-induced (DDI) genes were performed.
Mucosa were isolated at 02:00, 06:00, 10:00, 14:00, 18:00 and 22:00 from ileum of non-irradiated C3H/He mice keeping their daytime from 07:00 to 19:00. Relative levels in mRNAs for DDI genes (p21 and mdm2 as indicators for growth-arrest, bax and puma as indicators for apoptosis), clock genes (per1, per2, per3, cry1, clock and bmal1) and an indicator gene of crypt-growth (c-myb) to that of GAPDH gene were quantified by real-time RT-PCR. The message levels of all the clock genes fluctuated between 3 to 16-fold ranges periodically. The circadian changes at 2 to 3 fold in the mRNA levels were observed in c-myb, bax and puma genes. The peak clock times of c-myb, puma and bax mRNA were 02:00, 06:00 and 10:00, respectively. On the contrary, no obvious rhythm were detected in the message levels for p21 and mdm2. This implies that process after radiation damage in mucosa of small intestine are different in the profiles and degrees, and influenced by the circadian rhythm of mouse.
