Document Detail


Carotid body chemoreception in the absence and presence of CO2-HCO3-.
MedLine Citation:
PMID:  1667617     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Carotid body (CB) chemosensory responses to natural and pharmacological stimuli were studied in vitro in the presence and nominal absence of CO2-HCO3- in the perfusion-superfusion media. The CBs obtained from cats (n = 10), anesthetized with sodium pentobarbitone, were simultaneously perfused and superfused with a modified Tyrode solution at 36.5 +/- 0.5 degrees C, equilibrated respectively with PO2 of 120 and less than 20 Torr. The Tyrode, nominally free of CO2-HCO3- (HEPES-NaOH, pH 7.38, 310 mOsm), was used first. Subsequently the Tyrode containing HEPES-HCO3-, equilibrated with PCO2 of 36.8 Torr (pH 7.38) was used. Chemosensory discharges were recorded from the carotid sinus nerve. Both hypoxia (PO2 = 20-25 Torr) and ischemic hypoxia stimulated the discharge in the absence and presence of CO2-HCO3-. However, the presence of CO2-HCO3- significantly raised the baseline activity, augmented the speed, sensitivity and the maximal responses to both types of hypoxia. Hypercapnic perfusate (PCO2 = 65 Torr at pH 7.17) produced a peak response equally promptly in the absence and presence of CO2-HCO3- in the ongoing perfusate but generated a larger and more sustained response. Presence of CO2-HCO3- strongly potentiated the responses to cyanide (10(-10)-10(-7) mol) but less strikingly the responses to nicotine (10(-11)-10(-8) mol). Thus, the extracellular CO2-HCO3- significantly improved the response to hypoxia but was not essential for O2 chemoreception. The underlying mechanisms of the effect of CO2-HCO3- is likely to be mediated by the Cl(-)-HCO3- anion exchanger in the pH regulation of glomus cells.
Authors:
R Iturriaga; S Lahiri
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Brain research     Volume:  568     ISSN:  0006-8993     ISO Abbreviation:  Brain Res.     Publication Date:  1991 Dec 
Date Detail:
Created Date:  1992-06-23     Completed Date:  1992-06-23     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0045503     Medline TA:  Brain Res     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  253-60     Citation Subset:  IM    
Affiliation:
Department of Physiology, School of Medicine, University of Pennsylvania, Philadelphia 19104-6085.
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MeSH Terms
Descriptor/Qualifier:
Animals
Anoxia
Bicarbonates / pharmacology*
Carbon Dioxide / pharmacology*
Carotid Body / drug effects,  physiology*
Cats
Chemoreceptor Cells / drug effects,  physiology*
Dose-Response Relationship, Drug
Female
Male
Nicotine / pharmacology
Partial Pressure
Perfusion
Sodium Cyanide / pharmacology
Time Factors
Grant Support
ID/Acronym/Agency:
HL-19737/HL/NHLBI NIH HHS; HL-43413/HL/NHLBI NIH HHS
Chemical
Reg. No./Substance:
0/Bicarbonates; 124-38-9/Carbon Dioxide; 143-33-9/Sodium Cyanide; 54-11-5/Nicotine

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