| Popis: |
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 DependentR2*-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 24hperiod. Parallel with MRI scans, standard urinary and plasma parameters were quantified. Significant circadian variations of total renal blood flow were found over 24hwith 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. |
