Emans Tonja W, Janssen Ben J, Joles Jaap A, Krediet C T Paul
Department of Internal Medicine, Academic Medical Center at the University of AmsterdamAmsterdam, Netherlands.
Department of Nephrology and Hypertension, University Medical Center UtrechtUtrecht, Netherlands.
Front Physiol. 2017 Apr 6;8:205. doi: 10.3389/fphys.2017.00205. eCollection 2017.
Blood pressure, renal hemodynamics, electrolyte, and water excretion all display diurnal oscillation. Disturbance of these patterns is associated with hypertension and chronic kidney disease. Kidney oxygenation is dependent on oxygen delivery and consumption that in turn are determined by renal hemodynamics and metabolism. We hypothesized that kidney oxygenation also demonstrates 24-h periodicity. Telemetric oxygen-sensitive carbon paste electrodes were implanted in Sprague-Dawley rats (250-300 g), either in renal medulla ( = 9) or cortex ( = 7). Arterial pressure (MAP) and heart rate (HR) were monitored by telemetry in a separate group ( = 8). Data from 5 consecutive days were analyzed for rhythmicity by cosinor analysis. Diurnal electrolyte excretion was assessed by metabolic cages. During lights-off, oxygen levels increased to 105.3 ± 2.1% in cortex and 105.2 ± 3.8% in medulla. MAP was 97.3 ± 1.5 mmHg and HR was 394.0 ± 7.9 bpm during lights-off phase and 93.5 ± 1.3 mmHg and 327.8 ± 8.9 bpm during lights-on. During lights-on, oxygen levels decreased to 94.6 ± 1.4% in cortex and 94.2 ± 8.5% in medulla. There was significant 24-h periodicity in cortex and medulla oxygenation. Potassium excretion (1,737 ± 779 vs. 895 ± 132 μmol/12 h, = 0.005) and the distal Na/K exchange (0.72 ± 0.02 vs. 0.59 ± 0.02 < 0.001) were highest in the lights-off phase, this phase difference was not found for sodium excretion ( = 0.4). It seems that oxygen levels in the kidneys follow the pattern of oxygen delivery, which is known to be determined by renal blood flow and peaks in the active phase (lights-off).
血压、肾血流动力学、电解质及水排泄均呈现昼夜波动。这些模式的紊乱与高血压和慢性肾病相关。肾脏氧合依赖于氧输送和氧消耗，而氧输送和氧消耗又由肾血流动力学和代谢所决定。我们假设肾脏氧合也呈现24小时周期性。将遥测氧敏碳糊电极植入体重250 - 300克的Sprague-Dawley大鼠体内，其中9只植入肾髓质，7只植入肾皮质。另一组8只大鼠通过遥测监测动脉压（MAP）和心率（HR）。通过余弦分析对连续5天的数据进行节律性分析。利用代谢笼评估昼夜电解质排泄情况。在熄灯期间，皮质氧水平升至105.3±2.1%，髓质升至105.2±3.8%。熄灯期MAP为97.3±1.5 mmHg，HR为394.0±7.9次/分钟；开灯期MAP为93.5±1.3 mmHg，HR为327.8±8.9次/分钟。在开灯期间，皮质氧水平降至94.6±1.4%，髓质降至94.2±8.5%。肾皮质和髓质氧合存在显著的24小时周期性。钾排泄（1737±779对895±132 μmol/12小时，P = 0.005）和远端钠/钾交换（0.72±0.02对0.59±0.02，P < 0.001）在熄灯期最高，钠排泄未发现此相位差异（P = 0.4）。似乎肾脏中的氧水平遵循氧输送模式，已知氧输送由肾血流量决定并在活跃期（熄灯）达到峰值。
