Section of Radiology, Department of Surgical Sciences, University Hospital, Uppsala, Sweden.
Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden.
Am J Physiol Renal Physiol. 2020 Dec 1;319(6):F966-F978. doi: 10.1152/ajprenal.00311.2020. Epub 2020 Oct 19.
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 noninvasively 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 with MRI and to relate the findings to urinary excretions of electrolytes and markers of kidney function. Phase-contrast imaging, arterial spin labeling, and blood oxygen level-dependent transverse relaxation rate (R*) mapping were used to assess total renal blood flow and regional perfusion as well as intrarenal oxygenation in eight female and eight male healthy volunteers every fourth hour during a 24-h period. Parallel with MRI scans, standard urinary and plasma parameters were quantified. Significant circadian variations of total renal blood flow were found over 24 h, 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.
肾脏功能的昼夜节律调节参与维持全身内环境稳定，功能失调的昼夜节律可能与疾病的发展有关。磁共振成像（MRI）提供了可靠和可重复的肾功能无创性重复估计，而没有与造影剂和电离辐射相关的不良事件的风险。本研究的目的是使用 MRI 估计健康人体肾脏功能的昼夜变化，并将这些发现与电解质和肾功能标志物的尿液排泄相关联。相位对比成像、动脉自旋标记和血氧水平依赖横向弛豫率（R*）映射用于评估 8 名女性和 8 名男性健康志愿者在 24 小时期间每 4 小时一次的总肾血流量和区域灌注以及肾内氧合。与 MRI 扫描平行，量化了标准的尿液和血浆参数。在 24 小时内发现总肾血流量存在显著的昼夜变化，从中午到午夜血流量增加，夜间血流量减少。相比之下，未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均显示出昼夜变化，下午和晚上达到峰值。总之，估计来自电解质和废物排泄的总肾血流量和肾功能显示出明显的昼夜变化，而肾内氧合显示出明显较少的昼夜变化。
