Journal
AMERICAN JOURNAL OF PHYSIOLOGY-RENAL PHYSIOLOGY
Volume 316, Issue 4, Pages F635-F645Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajprenal.00254.2018
Keywords
intermittent hypoxia; oxygen tension; renal oxygen consumption; sodium transport efficiency
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Funding
- Department of Physiology, University College Cork, Ireland
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Chronic kidney disease (CKD) occurs in more than 50% of patients with obstructive sleep apnea (OSA). However, the impact of intermittent hypoxia (IH) on renal function and oxygen homeostasis is unclear. Male Sprague-Dawley rats were exposed to IH (270 s at 21% O-2; 90 s hypoxia, 6.5% O-2 at nadir) for 4 h [acute IH (AIH)] or to chronic IH (CIH) for 8 h/day for 2 wk. Animals were anesthetized and surgically prepared for the measurement of mean arterial pressure (MAP), and left renal excretory function, renal blood flow (RBF), and renal oxygen tension (PO2). AIH had no effect on MAP (123 +/- 14 vs. 129 +/- 14 mmHg, means +/- SE, sham vs. IH). The CIH group was hypertensive (122 +/- 9 vs. 144 +/- 15 mmHg, P < 0.05). Glomerular filtration rate (GFR) (0.92 +/- 0.27 vs. 1.33 +/- 0.33 ml/min), RBF (3.8 +/- 1.5 vs. 7.2 +/- 2.4 ml/min), and transported sodium (TNa) (132 +/- 39 vs. 201 +/- 47 mu mol/min) were increased in the AIH group (all P < 0.05). In the CIH group, GFR (1.25 +/- 0.28 vs. 0.86 +/- 0.28 ml/min, P < 0.05) and TNa (160 +/- 39 vs. 120 +/- 40 +/- mol/min, P < 0.05) were decreased, while RBF (4.13 +/- 1.5 vs. 3.08 +/- 1.5 ml/min) was not significantly different. Oxygen consumption (QO(2)) was increased in the AIH group (6.76 +/- 2.60 vs. 13.60 +/- 7.77 +/- mol/min, P < 0.05), but it was not significantly altered in the CIH group (3.97 +/- 2.63 vs. 6.82 +/- 3.29 +/- mol/min). Cortical PO2 was not significantly different in the AIH group (46 +/- 4 vs. 46 +/- 3 mmHg), but it was decreased in the CIH group (44 +/- 5 mmHg vs. 38 +/- 2 mmHg, P < 0.05). For AIH, renal oxygen homeostasis was preserved through a maintained balance between O-2 supply (RBF) and consumption (GFR). For CIH, mismatched TNa and QO(2) reflect inefficient O-2 utilization and, thereby, sustained decrease in cortical PO2.
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