1
|
Caldwell HG, Hoiland RL, Bain AR, Howe CA, Carr JMJR, Gibbons TD, Durrer CG, Tymko MM, Stacey BS, Bailey DM, Sekhon MS, MacLeod DB, Ainslie PN. Evidence for direct CO 2 -mediated alterations in cerebral oxidative metabolism in humans. Acta Physiol (Oxf) 2024; 240:e14197. [PMID: 38958262 DOI: 10.1111/apha.14197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 06/18/2024] [Accepted: 06/20/2024] [Indexed: 07/04/2024]
Abstract
AIM How the cerebral metabolic rates of oxygen and glucose utilization (CMRO2 and CMRGlc, respectively) are affected by alterations in arterial PCO2 (PaCO2) is equivocal and therefore was the primary question of this study. METHODS This retrospective analysis involved pooled data from four separate studies, involving 41 healthy adults (35 males/6 females). Participants completed stepwise steady-state alterations in PaCO2 ranging between 30 and 60 mmHg. The CMRO2 and CMRGlc were assessed via the Fick approach (CBF × arterial-internal jugular venous difference of oxygen or glucose content, respectively) utilizing duplex ultrasound of the internal carotid artery and vertebral artery to calculate cerebral blood flow (CBF). RESULTS The CMRO2 was altered by 0.5 mL × min-1 (95% CI: -0.6 to -0.3) per mmHg change in PaCO2 (p < 0.001) which corresponded to a 9.8% (95% CI: -13.2 to -6.5) change in CMRO2 with a 9 mmHg change in PaCO2 (inclusive of hypo- and hypercapnia). The CMRGlc was reduced by 7.7% (95% CI: -15.4 to -0.08, p = 0.045; i.e., reduction in net glucose uptake) and the oxidative glucose index (ratio of oxygen to glucose uptake) was reduced by 5.6% (95% CI: -11.2 to 0.06, p = 0.049) with a + 9 mmHg increase in PaCO2. CONCLUSION Collectively, the CMRO2 is altered by approximately 1% per mmHg change in PaCO2. Further, glucose is incompletely oxidized during hypercapnia, indicating reductions in CMRO2 are either met by compensatory increases in nonoxidative glucose metabolism or explained by a reduction in total energy production.
Collapse
Affiliation(s)
- Hannah G Caldwell
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
- Department of Anesthesiology, Pharmacology and Therapeutics, Vancouver General Hospital, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, British Columbia, Canada
- Collaborative Entity for REsearching Brain Ischemia (CEREBRI), University of British Columbia, Vancouver, British Columbia, Canada
| | - Anthony R Bain
- Department of Kinesiology, Faculty of Human Kinetics, University of Windsor, Windsor, Ontario, Canada
| | - Connor A Howe
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Jay M J R Carr
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Travis D Gibbons
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Cody G Durrer
- Centre for Physical Activity Research, Rigshospitalet, Copenhagen, Denmark
| | - Michael M Tymko
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, Vancouver General Hospital, University of British Columbia, Vancouver, British Columbia, Canada
- Human Cerebrovascular Physiology Laboratory, Department of Human Health and Nutritional Sciences, College of Biological Science, University of Guelph, Guelph, Ontario, Canada
| | - Benjamin S Stacey
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Pontypridd, UK
| | - Damian M Bailey
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Pontypridd, UK
| | - Mypinder S Sekhon
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, British Columbia, Canada
- Collaborative Entity for REsearching Brain Ischemia (CEREBRI), University of British Columbia, Vancouver, British Columbia, Canada
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, Vancouver General Hospital, University of British Columbia, Vancouver, British Columbia, Canada
- Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada
| | - David B MacLeod
- Human Pharmacology and Physiology Lab, Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| |
Collapse
|
2
|
Zhang K, Han Y, Gu F, Gu Z, Zhao J, Chen J, Chen B, Gao M, Hou Z, Yu X, Cai T, Gao Y, Xie J, Liu T, Liu K. Association between dietary total choline and abdominal aorta calcification among older US adults: A cross-sectional study of the National Health and Nutrition Examination Survey. JPEN J Parenter Enteral Nutr 2024; 48:155-164. [PMID: 37932919 DOI: 10.1002/jpen.2577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Revised: 10/23/2023] [Accepted: 10/26/2023] [Indexed: 11/08/2023]
Abstract
BACKGROUND Numerous studies indicate a potential bidirectional association between dietary choline intake and its derivative, betaine, and subclinical atherosclerosis. However, little research has been conducted on the relationship between dietary choline and severe abdominal aortic calcification (SAAC). METHODS This cross-sectional study analyzed population-based data from the National Health and Nutrition Examination Survey (2013-2014). Choline intake and food sources were measured using two 24-h dietary-recall interviews. The abdominal aortic calcification score was measured using a dual-emission x-ray absorptiometry scan. To assess the relationship between choline intake and SAAC, the study utilized restricted cubic spline and a multivariable logistic regression model. RESULTS Among the 2640 individuals included in the study, 10.9% had SAAC. After adjusting for all selected covariates, compared with the lowest quartile of dietary choline, the odds ratios of SAAC for the second-quartile, third-quartile, and fourth-quartile dietary choline intake were 0.63 (95% confidence interval [CI], 0.43-0.93), 0.63 (95% CI, 0.42-0.94), and 0.77 (95% CI, 0.5-1.16), respectively. The study found an L-shaped relationship between dietary choline and SAAC in the dose-response analysis. Subgroup analyses did not demonstrate any statistically significant interaction effects for any subgroup. CONCLUSION The study found that a higher intake of dietary choline is associated with a lower prevalence of SAAC. The dose-response analysis revealed an L-shaped relationship between dietary choline and SAAC. However, further studies are warranted to investigate the direct role of choline in the development of SAAC.
Collapse
Affiliation(s)
- Kai Zhang
- Cardiovascular Surgery Department of Jilin University Second Hospital, Changchun, China
| | - Yu Han
- Department of Ophthalmology, First Hospital of Jilin University, Changchun, China
| | - Fangmin Gu
- Cardiovascular Surgery Department of Jilin University Second Hospital, Changchun, China
| | - Zhaoxuan Gu
- Cardiovascular Surgery Department of Jilin University Second Hospital, Changchun, China
| | - JiaYu Zhao
- Cardiovascular Surgery Department of Jilin University Second Hospital, Changchun, China
| | - Jianguo Chen
- Bethune First College of Clinical Medicine, Jilin University, Changchun, China
| | - Bowen Chen
- Bethune First College of Clinical Medicine, Jilin University, Changchun, China
| | - Min Gao
- Department of Cancer Center, The First Hospital of Jilin University, Changchun, China
| | - Zhengyan Hou
- Bethune Second School of Clinical Medicine, Jilin University, Changchun, China
| | - Xiaoqi Yu
- Bethune Second School of Clinical Medicine, Jilin University, Changchun, China
| | - Tianyi Cai
- Bethune Second School of Clinical Medicine, Jilin University, Changchun, China
| | - Yafang Gao
- Bethune Second School of Clinical Medicine, Jilin University, Changchun, China
| | - Jinyu Xie
- Cardiovascular Surgery Department of Jilin University Second Hospital, Changchun, China
| | - Tianzhou Liu
- Department of Gastrointestinal Surgery, The Second Hospital of Jilin University, Changchun, China
| | - Kexiang Liu
- Cardiovascular Surgery Department of Jilin University Second Hospital, Changchun, China
| |
Collapse
|
3
|
Li Z, Tian Z. Restoration of autophagy activity by dipsacoside B alleviates exhaustive exercise-induced kidney injury via the AMPK/mTOR pathway. Nat Prod Res 2024:1-7. [PMID: 38293762 DOI: 10.1080/14786419.2024.2308002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2023] [Accepted: 01/16/2024] [Indexed: 02/01/2024]
Abstract
Exhaustive exercise (EE) induces kidney injury, but its concrete mechanism has not been fully elucidated. Hepatoprotective effects of dipsacoside B (DB) have been found previously, involving in autophagy induction. However, whether DB exerts renal protective effect and its potential mechanism are still unknown. The present study aimed to investigate the benefit of DB in EE-induced kidney injury and decipher its underlying mechanism. Here, we found that DB ameliorated EE-induced renal dysfunction and renal histopathological injury in rats. DB possessed anti-inflammatory, anti-oxidative, and anti-apoptotic functions in kidneys of exercise-induced exhausted rats. Besides, DB improved autophagy function in kidneys of EE rats. Mechanically, activation of the adenylate-activating protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway was implicated in the kidney injury-relieving effects and autophagy restoration induced by DB. Collectively, these findings provide reference for the clinical application of DB in preventing and managing EE-induced kidney injury.
Collapse
Affiliation(s)
- Zhenyu Li
- Sias University, Xinzheng, P.R. China
- The 521 Laboratory of Sports Physiology and Biochemistry, Department of Sport Science, College of Natural Science, Jeonbuk National University, Jeonju-si, Republic of Korea
| | - Zhuang Tian
- The 521 Laboratory of Sports Physiology and Biochemistry, Department of Sport Science, College of Natural Science, Jeonbuk National University, Jeonju-si, Republic of Korea
- College of Physical Education, Zhengzhou University, Zhengzhou, P.R. China
| |
Collapse
|
4
|
Mikulski T, Górecka M, Smorawiński J, Rachwalski K, Kryściak J, Nazar K, Ziemba AW. The effect of diminished metabolic acidosis on thermoregulatory response during exercise. Biol Sport 2024; 41:287-293. [PMID: 38188109 PMCID: PMC10765428 DOI: 10.5114/biolsport.2024.129475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 07/23/2022] [Accepted: 05/25/2023] [Indexed: 01/09/2024] Open
Abstract
It was reported that metabolic acidosis inhibits the activity of warm-sensitive hypothalamic neurons. The present study was designed to test the hypothesis that metabolic alkalosis may improve heat loss during intensive exercise in men. Fifteen male subjects aged 22-24 years were submitted to incremental exercise on two randomized occasions one week apart. During the bicarbonate trial exercise was preceded by ingestion of NaHCO3 at a dose 250 mg/kg whilst during the placebo trial lactose was administered. Exercise load was increased every 3 min by 30 W until volitional exhaustion. Ambient temperature was kept at 23-24°C and humidity 50-60%. Tympanic and skin temperatures were recorded and the rate of sweating was assayed by humidity measurement of nitrogen flowing through a capsule attached to the mid posterior chest. Total sweat loss was determined by the changes in body mass. Venous blood samples were taken before exercise and at the end of each workload for determination of acid-base parameters. The subjects attained similar maximal workload in the two tests (260 ± 6 W) with heart rate 185 ± 6 beats/min. Blood concentration of hydrogen ions was lower (p < 0.001) in the bicarbonate than in the placebo trial throughout the whole exercise period. There were no significant differences between these tests in tympanic and mean skin temperatures, sweating rate and total sweat loss. The present data showed that in men attenuation of metabolic acidosis by bicarbonate ingestion did not influence thermoregulation during incremental exercise performed until volitional exhaustion, possibly due to too short duration of exertional uncompensated metabolic acidosis.
Collapse
Affiliation(s)
- Tomasz Mikulski
- Clinical and Research Department of Applied Physiology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Warsaw, Poland
| | - Monika Górecka
- Clinical and Research Department of Applied Physiology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Warsaw, Poland
| | | | - Krzysztof Rachwalski
- University School of Physical Education, Department of Team Sports Games, Poznan, Poland
| | - Jakub Kryściak
- University School of Physical Education, Department of Physiology and Biochemistry, Poznan, Poland
| | - Krystyna Nazar
- Clinical and Research Department of Applied Physiology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Warsaw, Poland
| | - Andrzej W. Ziemba
- Clinical and Research Department of Applied Physiology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Warsaw, Poland
| |
Collapse
|
5
|
Carr JMJR, Day TA, Ainslie PN, Hoiland RL. The jugular venous-to-arterial P C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ difference during rebreathing and end-tidal forcing: Relationship with cerebral perfusion. J Physiol 2023; 601:4251-4262. [PMID: 37635691 DOI: 10.1113/jp284449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 08/11/2023] [Indexed: 08/29/2023] Open
Abstract
We examined two assumptions of the modified rebreathing technique for the assessment of the ventilatory central chemoreflex (CCR) and cerebrovascular CO2 reactivity (CVR), hypothesizing: (1) that rebreathing abolishes the gradient between the partial pressures of arterial and brain tissue CO2 [measured via the surrogate jugular venousP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ and arterialP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ difference (Pjv-a CO2 )] and (2) rebreathing eliminates the capacity of CVR to influence the Pjv-a CO2 difference, and thus affect CCR sensitivity. We also evaluated these variables during two separate dynamic end-tidal forcing (ETF) protocols (termed: ETF-1 and ETF-2), another method of assessing CCR sensitivity and CVR. Healthy participants were included in the rebreathing (n = 9), ETF-1 (n = 11) and ETF-2 (n = 10) protocols and underwent radial artery and internal jugular vein (advanced to jugular bulb) catheterization to collect blood samples. Transcranial Doppler ultrasound was used to measure middle cerebral artery blood velocity (MCAv). The Pjv-a CO2 difference was not abolished during rebreathing (6.2 ± 2.6 mmHg; P < 0.001), ETF-1 (9.3 ± 1.5 mmHg; P < 0.001) or ETF-2 (8.6 ± 1.4 mmHg; P < 0.001). The Pjv-a CO2 difference did not change during the rebreathing protocol (-0.1 ± 1.2 mmHg; P = 0.83), but was reduced during the ETF-1 (-3.9 ± 1.1 mmHg; P < 0.001) and ETF-2 (-3.4 ± 1.2 mmHg; P = 0.001) protocols. Overall, increases in MCAv were associated with reductions in the Pjv-a CO2 difference during ETF (-0.095 ± 0.089 mmHg cm-1 s-1 ; P = 0.001) but not during rebreathing (-0.028 ± 0.045 mmHg · cm-1 · s-1 ; P = 0.067). These findings suggest that, although the Pjv-a CO2 is not abolished during any chemoreflex assessment technique, hyperoxic hypercapnic rebreathing is probably more appropriate to assess CCR sensitivity independent of cerebrovascular reactivity to CO2 . KEY POINTS: Modified rebreathing is a technique used to assess the ventilatory central chemoreflex and is based on the premise that the rebreathing method eliminates the difference between arterial and brain tissueP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ . Therefore, rebreathing is assumed to isolate the ventilatory response to central chemoreflex stimulation from the influence of cerebral blood flow. We assessed these assumptions by measuring arterial and jugular venous bulbP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ and middle cerebral artery blood velocity during modified rebreathing and compared these data against data from another test of the ventilatory central chemoreflex using hypercapnic dynamic end-tidal forcing. The difference between arterial and jugular venous bulbP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ remained present during both rebreathing and end-tidal forcing tests, whereas middle cerebral artery blood velocity was associated with theP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ difference during end-tidal forcing but not rebreathing. These findings offer substantiating evidence that clarifies and refines the assumptions of modified rebreathing tests, enhancing interpretation of future findings.
Collapse
Affiliation(s)
- Jay M J R Carr
- Centre for Heart, Lung and Vascular Health, University of British Columbia Okanagan, Kelowna, BC, Canada
| | - Trevor A Day
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, AB, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, University of British Columbia Okanagan, Kelowna, BC, Canada
| | - Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, University of British Columbia Okanagan, Kelowna, BC, Canada
- Department of Anesthesiology, Pharmacology and Therapeutics, Vancouver General Hospital, University of British Columbia, Vancouver, BC, Canada
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, BC, Canada
| |
Collapse
|
6
|
Milloy KM, White MG, Chicilo JOC, Cummings KJ, Pfoh JR, Day TA. Assessing central and peripheral respiratory chemoreceptor interaction in humans. Exp Physiol 2022; 107:1081-1093. [PMID: 35766127 DOI: 10.1113/ep089983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2021] [Accepted: 06/16/2022] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? We investigated the interaction between central and peripheral respiratory chemoreceptors in healthy, awake human participants by (a) using a background of step increases in steady-state normoxic fraction of inspired carbon dioxide to alter central chemoreceptor activation and (b) using the transient hypoxia test to target the peripheral chemoreceptors. What is the main finding and its importance? Our data suggests that the central-peripheral respiratory chemoreceptor interaction is additive in minute ventilation and respiratory rate, but hypoadditive in tidal volume. Our study adds important new data in reconciling chemoreceptor interaction in awake healthy humans, and is consistent with previous reports of simple addition in intact rodents and humans. ABSTRACT Arterial blood gas levels are maintained through respiratory chemoreflexes, mediated by central (CCR) in the CNS and peripheral (PCR) chemoreceptors located in the carotid bodies. The interaction between central and peripheral chemoreceptors is controversial, and few studies have investigated this interaction in awake healthy humans, in part due to methodological challenges. We investigated the interaction between the CCRs and PCRs in healthy humans using a transient hypoxia test (three consecutive breaths of 100% N2 ; TT-HVR), which targets the stimulus and temporal domain specificity of the PCRs. TT-HVRs were superimposed upon three randomized background levels of steady-state inspired fraction of normoxic CO2 (FI CO2 ; 0, 0.02 and 0.04). Chemostimuli (calculated oxygen saturation; ScO2 ) and respiratory variable responses (respiratory rate, inspired tidal volume and ventilation; RR , VTI , V̇I ), were averaged from all three TT-HVR trials at each FI CO2 level. Responses were assessed as (a) a change from BL (delta; ∆) and (b) indexed against ∆ScO2 . Aside from a significantly lower ∆VTI response in 0.04 FI CO2 (P = 0.01), the hypoxic rate responses (∆RR or ∆RR /∆ScO2 ; P = 0.46, P = 0.81), hypoxic tidal volume response (∆VTI /∆ScO2 ; P = 0.08) and the hypoxic ventilatory responses (∆V̇I and (∆V̇I /∆ScO2 ; P = 0.09 and P = 0.31) were not significantly different across FI CO2 trials. Our data suggests simple addition between central and peripheral chemoreceptors in V̇I , which is mediated through simple addition in RR responses, but hypo-addition in VTI responses. Our study adds important new data in reconciling chemoreceptor interaction in awake healthy humans, and is consistent with previous reports of simple addition in intact rodents and humans. This article is protected by copyright. All rights reserved.
Collapse
Affiliation(s)
- Kristin M Milloy
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Canada
| | - Matthew G White
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Canada
| | - Janelle O C Chicilo
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Canada
| | | | - Jamie R Pfoh
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Canada
| | - Trevor A Day
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Canada
| |
Collapse
|
7
|
Caldwell HG, Carr JMJR, Minhas JS, Swenson ER, Ainslie PN. Acid-base balance and cerebrovascular regulation. J Physiol 2021; 599:5337-5359. [PMID: 34705265 DOI: 10.1113/jp281517] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 10/19/2021] [Indexed: 12/22/2022] Open
Abstract
The regulation and defence of intracellular pH is essential for homeostasis. Indeed, alterations in cerebrovascular acid-base balance directly affect cerebral blood flow (CBF) which has implications for human health and disease. For example, changes in CBF regulation during acid-base disturbances are evident in conditions such as chronic obstructive pulmonary disease and diabetic ketoacidosis. The classic experimental studies from the past 75+ years are utilized to describe the integrative relationships between CBF, carbon dioxide tension (PCO2 ), bicarbonate (HCO3 - ) and pH. These factors interact to influence (1) the time course of acid-base compensatory changes and the respective cerebrovascular responses (due to rapid exchange kinetics between arterial blood, extracellular fluid and intracellular brain tissue). We propose that alterations in arterial [HCO3 - ] during acute respiratory acidosis/alkalosis contribute to cerebrovascular acid-base regulation; and (2) the regulation of CBF by direct changes in arterial vs. extravascular/interstitial PCO2 and pH - the latter recognized as the proximal compartment which alters vascular smooth muscle cell regulation of CBF. Taken together, these results substantiate two key ideas: first, that the regulation of CBF is affected by the severity of metabolic/respiratory disturbances, including the extent of partial/full acid-base compensation; and second, that the regulation of CBF is independent of arterial pH and that diffusion of CO2 across the blood-brain barrier is integral to altering perivascular extracellular pH. Overall, by realizing the integrative relationships between CBF, PCO2 , HCO3 - and pH, experimental studies may provide insights to improve CBF regulation in clinical practice with treatment of systemic acid-base disorders.
Collapse
Affiliation(s)
- Hannah G Caldwell
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan, Kelowna, Canada
| | - Jay M J R Carr
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan, Kelowna, Canada
| | - Jatinder S Minhas
- Cerebral Haemodynamics in Ageing and Stroke Medicine (CHiASM) Research Group, NIHR Leicester Biomedical Research Centre, University of Leicester, Leicester, UK
| | - Erik R Swenson
- Pulmonary, Critical Care and Sleep Medicine Division, University of Washington, and VA Puget Sound Healthcare System, Seattle, WA, USA
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan, Kelowna, Canada
| |
Collapse
|