Abstract: AIM: To explore the expression of PER 2 (Period 2) protein, one clock protein, in aorta and myocardiums from Sprague-Dawley(SD) rats and spontaneous hypertensive rats(SHR).Methods: Spontaneous hypertensive rats and SD rats were housed in a dark room for 36 h, followed by a strict 12 h light 12 h dark cycle regimen for 2 weeks (lights on at 09:00, zeitgeber time [ZT] 0).On the day of experiment, rats were sacriticed every 4 h.The expression of PER 2 protein was detected by Western blot analysis.Results: PER 2 protein expression exhibited a rhythm of approximately 24 h in normal myocardium and aorta, and its expression in hypertrophic myocardium and aorta also exhibited this rhythm. However, PER 2 protein expression of SHR was significantly higher than that of normal rats.Conclusion: There might be a positive relationship between hypertension-induced myocardial hypertrophy and aortal disorder and the enhancement of expression of clock protein.

Key words: clock gene, PER 2, hypertension, myocardium, aorta