The influence of altered light–dark cycles on circadian rhythms of blood biomarkers in Wistar rats

Apr 6, 2026Chronobiology international

Changed light and dark cycles affect daily patterns of blood markers in Wistar rats

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Abstract

A total of 120 Wistar rats were exposed to different lighting conditions over 21 days, resulting in significant alterations to their biochemical parameters.

Continuous illumination led to the disappearance of daily fluctuations in most biochemical parameters.
A shift-work-like lighting regimen caused statistically significant changes in circadian rhythm characteristics, including acrophase shifts.
Changes in amplitude were observed for most biochemical parameters, except for LDH and creatinine, which showed no significant rhythms.
More pronounced effects on biochemical parameters were noted under the simulated shift-work schedule compared to continuous illumination.

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Since the effect of light-dark cycle disruption on the structure of biological rhythms generally is well known, the study focused on the effect of different light patterns on biochemical parameters and their circadian rhythms. A total of 120 Wistar rats were allocated into three experimental groups ( = 40/group) for a period of 21 days. The control group was housed under a standard 10:14h light-dark schedule (lights on: 08:00). Group I was exposed to continuous illumination (dark deprivation). Group II underwent a shift-work-like lighting regimen, consisting of 24-h light exposure followed by 2 days of a standard light-dark cycle. A three-week exposure resulted in the disappearance of statistically significant daily fluctuations for most of the studied parameters. In addition, most biochemical parameters showed statistically significant changes in the characteristics of the circadian rhythm: an acrophase shift and an increase or decrease in amplitude, with the exception of LDH and creatinine, for which no significant rhythms were detected in the experimental groups. This study demonstrated that both experimental lighting regimens significantly altered the values of the investigated parameters, with more pronounced effects observed under the simulated shift-work schedule. n

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The influence of altered light–dark cycles on circadian rhythms of blood biomarkers in Wistar rats

Abstract

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