Biodistribution of 131I in mice is influenced by circadian variations

Charlotte K Andersson,Eva B Forssell-Aronsson,Mikael Elvborn,Britta Langen,Johan K E Spetz

doi:10.1038/s41598-020-72180-7

Charlotte K Andersson, Eva B Forssell-Aronsson + Show 3 more

Open Access

https://doi.org/10.1038/s41598-020-72180-7

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Abstract

Effects of radiation and biodistribution of radionuclides are often studied in animal models. Circadian rhythm affects many biological functions and may influence the biokinetics of radionuclides and observed responses. The aim of this study was to investigate if the time during the day of 131I injection affects the biodistribution and absorbed dose to tissues in mice. Biodistribution studies were conducted on male C57BL/6 N mice for three diurnal time-series: the animals were i.v. injected with 160 kBq 131I at 8 am, 12 pm or 4 pm. The activity concentration in organs and tissues was measured at 1 h to 7 days after administration and absorbed dose at day 7 was determined. Comparison between the three time-series showed statistically significant differences in activity concentration in all investigated tissues and organs. Administration performed at 12 pm resulted in general in higher absorbed dose to the organs than injection performed at 8 am and 4 pm. Time of day of administration affects the biodistribution of 131I in mice and consequently the absorbed dose to individual organs. These findings advocate that subsequent biodistribution studies and dosimetry calculations should consider time-point of administration as a variable that could influence the results.

Highlights

Effects of radiation and biodistribution of radionuclides are often studied in animal models
Through hormones and the neuronal system, the suprachiasmatic nucleus (SCN) in turn synchronizes the timing of oscillators in peripheral organs, where the hypothalamus-pituitary-thyroid (HPT) axis is an example of an endocrine feedback loop that is known to have a circadian r hythm[8]
Significant differences were observed between the 8 am and 12 pm groups at 4 h p.i., 0.77 (SEM = 0.47) vs. 3.9 (SEM = 0.6), respectively (p = 0.018)

Summary

Introduction

Effects of radiation and biodistribution of radionuclides are often studied in animal models. The aim of this study was to investigate if the time during the day of 131I injection affects the biodistribution and absorbed dose to tissues in mice. Time of day of administration affects the biodistribution of 131I in mice and the absorbed dose to individual organs. Sleep/wake cycle, and body temperature, as well as secretion of hormones like thyroid stimulating hormone (TSH), insulin, and melatonin are but a few examples of processes that follow a circadian rhythm[6] These time-related processes are regulated by a system of endogenous biological clocks, i.e. a time-keeping network[7]. The purpose of this study was to investigate if time of day of injection affects the biodistribution/biokinetics of 131I and the absorbed dose to organs and tissues in mice

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