Chronobiological Aspects of Preconditioning by Systemic Asphyxia – Endogenous Cardioprotection?

Biochemistry and Biophysics

Pavol Svorc¹ 

关键词: Chronobiology;    Preconditioning;    Systemic Asphyxia;    Electrical Stability of the Heart;    Rat;   

DOI  :  

学科分类：生物化学/生物物理

来源: Science and Engineering Publishing Company

【 摘 要 】

Abstract: There is evidence that repeating brief periods of myocardial ischemia and reperfusion may provide protection against electrical instability of the heart evoked by subsequent ischemia/reperfusion injury. Similar cardioprotective effectshave been obtained after pre-treatment with repetitive episodes of hypoxia. We focused to fact whether there are differences in the conditions and dynamics of the developing protective effects of myocardial preconditioning applied during the light (nonactive) and dark (active) parts of the day regimen of rats, and to obtain an understanding concerning chronophysiological aspects of this phenomenon in in vivo rat experiments.The experiments were performed in anaesthetized (ketamine/xylazine anaesthesia, 100 mg/kg + 15 mg/kg, i.m., open chest experiments)after adaptation to a LD cycle of 12h : 12h, with the dark part of day from 06:00 to 18:00hfor 4 weeks. The ventricular arrhythmia threshold (VAT) was estimated by direct electrical stimulation of the heart. Animals were artificially ventilated by humified room air at the parameters of the initial ventilation and reoxygenation: respiratory rate, 40 breaths/min; and tidal volume, 1 ml/100g b.w. During experimental hypoventilatory asphyxia, the respiratory rate and tidal volume were reduced to 20 breaths/min and 0.5 ml/100g b.w., respectively. One cycle of preconditioning by asphyxia is too weak of a stimulus for the production of cardioprotection in both light parts of the day.The cardioprotection probably starts after two cycles of preconditioning by asphyxia in both light parts, and the cardioprotective effect of preconditioning by asphyxia depends on the numbers of the preconditioning cycles and in the dependence on LD cycle - it is highlight by three cycles of preconditioning by asphyxia. It is concluded that there are different reactions of the rat myocardium for the asphyxic preconditioning in the dependence on the LD cycle.

【 授权许可】

Unknown