Renal reactivity: acid-base compensation during incremental ascent to high altitude.

Autor: Zouboules SM; Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada., Lafave HC; Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada., O'Halloran KD; University College Cork, Cork, Ireland., Brutsaert TD; University of Syracuse, Syracuse, NY, USA., Nysten HE; Red Deer Regional Hospital, Red Deer, Alberta, Canada., Nysten CE; Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada., Steinback CD; Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, Alberta, Canada., Sherpa MT; Kunde Hospital, Khunde, Solukhumbu, Nepal., Day TA; Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada.
Jazyk: angličtina
Zdroj: The Journal of physiology [J Physiol] 2018 Dec; Vol. 596 (24), pp. 6191-6203. Date of Electronic Publication: 2018 Oct 28.
DOI: 10.1113/JP276973
Abstrakt: Key Points: Ascent to high altitude imposes an acid-base challenge in which renal compensation is integral for maintaining pH homeostasis, facilitating acclimatization and helping prevent mountain sicknesses. The time-course and extent of plasticity of this important renal response during incremental ascent to altitude is unclear. We created a novel index that accurately quantifies renal acid-base compensation, which may have laboratory, fieldwork and clinical applications. Using this index, we found that renal compensation increased and plateaued after 5 days of incremental altitude exposure, suggesting plasticity in renal acid-base compensation mechanisms. The time-course and extent of plasticity in renal responsiveness may predict severity of altitude illness or acclimatization at higher or more prolonged stays at altitude.
Abstract: Ascent to high altitude, and the associated hypoxic ventilatory response, imposes an acid-base challenge, namely chronic hypocapnia and respiratory alkalosis. The kidneys impart a relative compensatory metabolic acidosis through the elimination of bicarbonate (HCO 3 - ) in urine. The time-course and extent of plasticity of the renal response during incremental ascent is unclear. We developed an index of renal reactivity (RR), indexing the relative change in arterial bicarbonate concentration ([HCO 3 - ] a ) (i.e. renal response) against the relative change in arterial pressure of CO 2 ( P aC O 2 ) (i.e. renal stimulus) during incremental ascent to altitude ( Δ [ HC O 3 - ] a / Δ P aC O 2 ). We aimed to assess whether: (i) RR magnitude was inversely correlated with relative changes in arterial pH (ΔpH a ) with ascent and (ii) RR increased over time and altitude exposure (i.e. plasticity). During ascent to 5160 m over 10 days in the Nepal Himalaya, arterial blood was drawn from the radial artery for measurement of blood gas/acid-base variables in lowlanders at 1045/1400 m and after 1 night of sleep at 3440 m (day 3), 3820 m (day 5), 4240 m (day 7) and 5160 m (day 10) during ascent. At 3820 m and higher, RR significantly increased and plateaued compared to 3440 m (P < 0.04), suggesting plasticity in renal acid-base compensations. At all altitudes, we observed a strong negative correlation (r ≤ -0.71; P < 0.001) between RR and ΔpH a from baseline. Renal compensation plateaued after 5 days of altitude exposure, despite subsequent exposure to higher altitudes. The time-course, extent of plasticity and plateau in renal responsiveness may predict severity of altitude illness or acclimatization at higher or more prolonged stays at altitude.
(© 2018 The Authors. The Journal of Physiology © 2018 The Physiological Society.)
Databáze: MEDLINE
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