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Correlation between convection requirement and carotid body responses to hypoxia and hemoglobin affinity: comparison between two rat strains. J Comp Physiol B 2021; 191:1031-1045. [PMID: 33970341 DOI: 10.1007/s00360-021-01377-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 03/31/2021] [Accepted: 04/13/2021] [Indexed: 02/06/2023]
Abstract
We tested the hypothesis that differences in ventilatory ([Formula: see text]) or convection requirement ([Formula: see text]/[Formula: see text]O2) response to hypoxia would be correlated with differences in hemoglobin (Hb) oxygen affinity between two strains of rats, as they have been shown to be among several species of mammals, birds and reptiles. Brown Norway (BN) rats reduce metabolism more than they increase ventilation in response to hypoxia and both the ventilatory and convection requirement responses to hypoxia are lower in the BN than the Sprague-Dawley (SD) rat. The lower threshold of the ventilation/convection requirement responses of the BN to hypoxia are associated with a higher affinity Hb than the SD rats, (P50 values of 32.4 (± 0.6) versus 34.4 (± 0.5), respectively (P < 0.05), and P75 values of 46.1 (± 0.5) for BN versus 50.7 (± 0.8) for SD (P < 0.001). This significant difference, particularly near the inflection point of the dissociation curve, supported our hypothesis. A reduced sensitivity of BN compared to SD carotid bodies was found. BN carotid bodies (from 36 20-60-day-olds) had a mean estimated volume of 26.64 ± 1.47 × 106 μm3, significantly (P < 0.0001) smaller than SD carotid bodies (from 46 16-40-day-olds) at 50.66 ± 3.41 × 106 μm3. Both genetic and epigenetic/developmental mechanisms may account for the observed inter-strain differences.
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Mosqueira M, Iturriaga R. Chronic hypoxia changes gene expression profile of primary rat carotid body cells: consequences on the expression of NOS isoforms and ET-1 receptors. Physiol Genomics 2019; 51:109-124. [DOI: 10.1152/physiolgenomics.00114.2018] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Sustained chronic hypoxia (CH) produces morphological and functional changes in the carotid body (CB). Nitric oxide (NO) and endothelin-1 (ET-1) play a major role as modulators of the CB oxygen chemosensory process. To characterize the effects of CH related to normoxia (Nx) on gene expression, particularly on ET-1 and NO pathways, primary cultures of rat CB cells were exposed to 7 days of CH. Total RNA was extracted, and cDNA-32P was synthesized and hybridized with 1,185 genes printed on a nylon membrane Atlas cDNA Expression Array. Out of 324 differentially expressed genes, 184 genes were upregulated, while 140 genes were downregulated. The cluster annotation and protein network analyses showed that both NO and ET-1 signaling pathways were significantly enriched and key elements of each pathway were differentially expressed. Thus, we assessed the effect of CH at the protein level of nitric oxide synthase (NOS) isoforms and ET-1 receptors. CH induced an increase in the expression of endothelial NOS, inducible NOS, and ETB. During CH, the administration of SNAP, a NO donor, upregulated ETB. Treatment with Tezosentan (ET-1 receptor blocker) during CH upregulated all three NOS isoforms, while the NOS blocker L-NAME induced upregulation of iNOS and ETB and downregulated the protein levels of ETA. These results show that CH for 7 days changed the cultured cell CB gene expression profile, the NO and ET-1 signaling pathways were highly enriched, and these two signaling pathways interfered with the protein expression of each other.
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Affiliation(s)
- Matías Mosqueira
- Laboratorio de Neurobiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago Chile
- Cardio-Ventilatory Muscle Physiology Laboratory, Institute of Physiology and Pathophysiology, Heidelberg University Hospital, Heidelberg, Germany
| | - Rodrigo Iturriaga
- Laboratorio de Neurobiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago Chile
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Fink AM, Topchiy I, Ragozzino M, Amodeo DA, Waxman JA, Radulovacki MG, Carley DW. Brown Norway and Zucker Lean rats demonstrate circadian variation in ventilation and sleep apnea. Sleep 2014; 37:715-21. [PMID: 24899760 DOI: 10.5665/sleep.3576] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
STUDY OBJECTIVES Circadian rhythms influence many biological systems, but there is limited information about circadian and diurnal variation in sleep related breathing disorder. We examined circadian and diurnal patterns in sleep apnea and ventilatory patterns in two rat strains, one with high sleep apnea propensity (Brown Norway [BN]) and the other with low sleep apnea propensity (Zucker Lean [ZL]). DESIGN/SETTING Chronically instrumented rats were randomized to breathe room air (control) or 100% oxygen (hyperoxia), and we performed 20-h polysomnography beginning at Zeitgeber time 4 (ZT 4; ZT 0 = lights on, ZT12 = lights off). We examined the effect of strain and inspired gas (twoway analysis of variance) and analyzed circadian and diurnal variability. MEASUREMENTS AND RESULTS Strain and inspired gas-dependent differences in apnea index (AI; apneas/h) were particularly prominent during the light phase. AI in BN rats (control, 16.9 ± 0.9; hyperoxia, 34.0 ± 5.8) was greater than in ZL rats (control, 8.5 ± 1.0; hyperoxia, 15.4 ± 1.1, [strain effect, P < 0.001; gas effect, P = 0.001]). Hyperoxia reduced respiratory frequency in both strains, and all respiratory pattern variables demonstrated circadian variability. BN rats exposed to hyperoxia demonstrated the largest circadian fluctuation in AI (amplitude = 17.9 ± 3.7 apneas/h [strain effect, P = 0.01; gas effect, P < 0.001; interaction, P = 0.02]; acrophase = 13.9 ± 0.7 h; r (2) = 0.8 ± 1.4). CONCLUSIONS Inherited, environmental, and circadian factors all are important elements of underlying sleep related breathing disorder. Our method to examine sleep related breathing disorder phenotypes in rats may have implications for understanding vulnerability for sleep related breathing disorder in humans.
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Affiliation(s)
- Anne M Fink
- Center for Narcolepsy, Sleep and Health Research, College of Nursing, University of Illinois at Chicago, Chicago, IL ; Department of Biobehavioral Health Science, College of Nursing, University of Illinois at Chicago, Chicago, IL
| | - Irina Topchiy
- Center for Narcolepsy, Sleep and Health Research, College of Nursing, University of Illinois at Chicago, Chicago, IL ; Department of Biobehavioral Health Science, College of Nursing, University of Illinois at Chicago, Chicago, IL ; Department of Medicine, University of Illinois at Chicago, Chicago, IL
| | - Michael Ragozzino
- Department of Psychology, University of Illinois at Chicago, Chicago, IL
| | - Dionisio A Amodeo
- Department of Psychology, University of Illinois at Chicago, Chicago, IL
| | - Jonathan A Waxman
- Center for Narcolepsy, Sleep and Health Research, College of Nursing, University of Illinois at Chicago, Chicago, IL ; Department of Bioengineering, University of Illinois at Chicago, Chicago, IL
| | - Miodrag G Radulovacki
- Center for Narcolepsy, Sleep and Health Research, College of Nursing, University of Illinois at Chicago, Chicago, IL ; Department of Pharmacology, University of Illinois at Chicago, Chicago, IL
| | - David W Carley
- Center for Narcolepsy, Sleep and Health Research, College of Nursing, University of Illinois at Chicago, Chicago, IL ; Department of Biobehavioral Health Science, College of Nursing, University of Illinois at Chicago, Chicago, IL ; Department of Medicine, University of Illinois at Chicago, Chicago, IL
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