Aims: 

The investigation of factors modulating cardiac susceptibility to ischaemia-reperfusion (I/R) remains a current topic of experimental cardiology. Although it is known that continuous light exposure influences cardiovascular system, its effects on cardiac I/R sensitivity, morphology and NO-synthase (NOS) have been less intensively investigated.

Methods: 

Two groups of male adult Wistar rats were investigated (n = 15 each): controls exposed to normal light/dark cycle and rats exposed to continuous light for 4 weeks. Perfused isolated hearts (Langendorff tech.) were exposed to 25min global ischaemia and subsequent 30min reperfusion. The recovery of functional parameters (coronary flow, left ventricular developed pressure, and contractility and relaxation index) during reperfusion as well as the incidence, severity and duration of arrhythmias during the first 10 minutes of reperfusion were determined. Non-perfused hearts were used for NOS activity and (endothelial and inducible isoform) expression, conjugated dienes (CD) concentration, fibrosis and collagen I/III ratio determination.

Results: 

The hearts from rats exposed to continuous light showed more rapid recovery of functional parameters, but the incidence, duration and severity of reperfusion arrhythmias were higher in this group. The NOS activity was attenuated and collagen I/III ratio increased, while the level of fibrosis, concentration of CD and NOS expressions remained unaffected by light exposure.

Conclusion: 

Continuous light exposure of rats modified myocardial structure and cardiac response to I/R. This effect could be at least partially mediated by the simultaneously observed attenuation of NOS activity. (GUK 29/2007, APVT 51-027404, 51-018004, VEGA 1/3429/06, 2/6148/26, 2/5110/25, SP 51/0280900/0280901)