Circadian regulation of kidney function is involved in maintaining whole-body homeostasis and dysfunctional circadian rhythm can potentially be involved in disease development. Magnetic Resonance Imaging (MRI) provides reliable and reproducible repetitive estimates of kidney function non-invasively without the risk of adverse events associated with contrast agents and ionizing radiation. The purpose of this study was to estimate circadian variations in kidney function in healthy human subjects using MRI, and relate the findings with urinary excretions of electrolytes and markers of kidney function. Phase Contrast imaging, Arterial Spin Labeling and Blood Oxygen Level Dependent R₂^*-mapping were used to assess the total renal blood flow and regional perfusion, and intrarenal oxygenation in eight female and eight male healthy volunteers every fourth hour during a 24h period. Parallel with MRI scans, standard urinary and plasma parameters were quantified. Significant circadian variations of total renal blood flow were found over 24h with increasing flow from noon to midnight and decreasing flow during the night. In contrast, no circadian variation in intrarenal oxygenation was detected. Urinary excretions of electrolytes, osmotically active particles, creatinine and urea all displayed circadian variations, peaking during the afternoon and evening hours. In conclusion, total renal blood flow and kidney function, as estimated from excretion of electrolytes and waste products, display profound circadian variations, whereas intrarenal oxygenation displays significantly less circadian variation.

中文翻译：

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使用非侵入性磁共振成像监测健康志愿者肾血流量和肾功能的昼夜变化

肾功能的昼夜节律调节与维持全身稳态有关，而功能失调的昼夜节律可能与疾病发展有关。磁共振成像 (MRI) 以无创方式提供可靠且可重复的肾功能重复估计，没有与造影剂和电离辐射相关的不良事件风险。本研究的目的是使用 MRI 估计健康人类受试者肾功能的昼夜节律变化，并将这些发现与电解质的尿液排泄和肾功能标志物联系起来。相衬成像、动脉自旋标记和血氧水平相关 R ₂ ^*-mapping 用于在 24 小时内每 4 小时评估 8 名女性和 8 名男性健康志愿者的总肾血流量和区域灌注以及肾内氧合情况。与 MRI 扫描平行，对标准尿液和血浆参数进行量化。在 24 小时内发现总肾血流量有显着的昼夜节律变化，中午至午夜流量增加，夜间流量减少。相反，没有检测到肾内氧合的昼夜变化。电解质、渗透活性颗粒、肌酐和尿素的尿排泄都显示出昼夜节律变化，在下午和晚上达到峰值。总之，根据电解质和废物排泄估计的总肾血流量和肾功能显示出显着的昼夜节律变化，