Changes of cardiac catecholamines in rats after repeated +Gz exposures and protective effects of low-G preconditioning and tea polyphenols.

OBJECTIVE

To observe whether repeated +Gz exposures could induce metabolic disorder of cardiac catecholamines in rats as well as the protective effects of low-G preconditioning and tea polyphenols (TP).

METHOD

Thirty-two male Wistar rats were randomly divided into 4 groups (n=8): group A (control), only submitted to +1 Gz 5 min; group B (+10 Gz stress), exposed to +10 Gz 30 s, 5 times/d with +1 Gz 1 min interval, 3 d/wk, for 3 wk in total; group C (low G preconditioning), +Gz stress parameters were the same to that of group B, but the rats were submitted to +2 Gz 5 min 1 h prior to +10 Gz exposure; group D (TP protection), + Gz stress parameters were the same to that of group B, but TP was given orally to the rats at the dose of 200 mg/kg 1 h prior to +10 Gz exposure. These animals were decapitated on the next morning of the last centrifuge run, and the hearts were taken out and stored in liquid nitrogen immediately. The contents of noradrenaline (NA), adrenaline (AD), dopamine (DA) and serotonin (5-HT) in myocardial tissue were determined using HPLC with electrochemical detector.

RESULT

Compared with group A, AD level in group B increased significantly (P < 0.01), but there were no significant differences of NA, DA and 5-HT contents between the two groups. Compared with group B, the myocardial contents of AD and 5-HT were decreased significantly in group C and D (P<0.01), while myocardial DA concentration in group D increased significantly (P<0.01).

CONCLUSION

Repeated +10 Gz exposures could induce metabolic disorder of catecholamines in rat heart, especially the increase of AD level. Low-G preconditioning and natural antioxidant TP had significant protective effects.