What is the central question of this study? Artificial light at night decreases blood pressure and heart rate in rats. Are mentioned changes in heart rate accompanied by changes in protein expression in the heart's left ventricle? What is the main finding and its importance? For the first time, we reported that five weeks of artificial light at night affected protein expression in the heart's left ventricle in normotensive and hypertensive rats. Artificial light at night decreased expression of the sarco/endoplasmic reticulum Ca2+ -ATPase, angiotensin II receptor type 1, and endothelin-1.
Artificial light at night (ALAN) affects the circadian rhythm of the heart rate in normotensive Wistar (WT) and spontaneously hypertensive rats (SHR) through the autonomic nervous system, which regulates the heart's activity through calcium handling, an important regulator in heart contractility. We analysed the expression of the sarco/endoplasmic reticulum Ca2+ -ATPase (SERCA2) and other selected regulatory proteins involved in the regulation of heart contractility, angiotensin II receptor type 1 (AT1 R), endothelin-1 (ET-1) and tyrosine hydroxylase (TH) in the left ventricle of the heart in WT and SHR after two and five weeks of ALAN with intensity 1-2 lx. Expression of SERCA2 was decreased in WT (control: 0.53 ± 0.07; ALAN: 0.46 ± 0.10) and SHR (control: 0.72 ± 0.18; ALAN: 0.56 ± 0.21) after five weeks of ALAN (p = 0.067). Expression of AT1 R was significantly decreased in WT (control: 0.51 ± 0.27; ALAN: 0.34 ± 0.20) and SHR (control: 0.38 ± 0.07; ALAN: 0.23 ± 0.09) after two weeks of ALAN (p = 0.028) and in SHR after five weeks of ALAN. Expression of ET-1 was decreased in WT (control: 0.51 ± 0.27; ALAN: 0.28 ± 0.12) and SHR (control: 0.54 ± 0.10; ALAN: 0.35 ± 0.23) after five weeks of ALAN (p = 0.015). ALAN did not affect the expression of TH in WT or SHR. In conclusion, ALAN suppressed the expression of SERCA2, AT1 R and ET-1, which are important for the regulation of heart contractility, in a strain-dependent pattern in both WT and SHR. This article is protected by copyright. All rights reserved.