ABSTRACT
Recently circadian clock genes have been identified in humans but information regarding their expression has remained very limited. The evaluation of circadian variations in the expression of clock genes in humans seems to be a major importance both from a fundamental point of view as a diagnostic and therapeutic perspective. In this context, several works including ours have described the fluctuation of clock genes. Describing rhythmic expression of clock genes in intensive care units patients during 24h and we tried to determine the effect of the absence of synchronizers such as light/ dark cycle on these rhythms. 15 patients received care in private room in intensive care units in the hospital Sahloul [5 comatous and 10 non comatous patients]. For RNA isolation we used peripheral blood mononuclear cells which represent an ideal material to investigate non-invasively the human clock at the molecular level. In the present study, we noticed that clock genes mRNA exhibit a circadian expression in comatose patients, while the rhythmicity of some studied genes disappeared in non-comatose patients. The disturbance of the rhythmic fluctuation of the clock genes could be the result of the effect of surgery on some biological rhythms as it could be explained by the lack of synchronizers in intensive care units such as light/dark cycle