Carbon Dioxide — Essential Ingredient for in vivo Carotid Body Chemotransduction
The carotid body responds to the changes in arterial Po2, Pco2, and pH. Although different mechanisms have been suggested for the chemotransduction of hypoxia and hypercapnia in the carotid body, it is also true that the response of the carotid body to one stimuli is not totally independent of other stimuli. Several studies have shown that lowering arterial Pco2 can dramatically reduce the carotid body response to hypoxia2, 3, 4, 5. In addition, we have recently demonstrated that, whereas selective perfusion of the carotid body with hypoxic perfusate containing CO2/HCO3 - increased carotid chemoreceptor neural activity, perfusion with CO2/HCO3 --free hypoxic perfusate did not This suggested a crucial role for CO2/HCO3 - in hypoxic chemotransduction7. Pertinent to these studies a recent report showed that intracellular pH of the type I cell from the rat carotid body was very alkalotic in the CO2/HCO3 --free media1. Based on these findings we hypothesized that CO2/HCO3 - plays a fundamental role for the carotid body chemotransduction, possibly as an essential ingredient in the regulatory mechanisms of intracellular pH (pH/) in the chemosensitive unit. Decrease in CO2/HCO3 - would increase pH/ of the chemosensitive unit. Alkalinization of the unit would turn off the process of chemotransduction. We tested this hypothesis using a technique of in vivo selective perfusion of the carotid body.
KeywordsCarotid Body Sodium Butyrate Krebs Ringer Bicarbonate Carotid Sinus Nerve HEPES Buffer Solution
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
Buckler, K. J., R. D. Vaughan-Jones, C. Peers, and P. C. G. Nye. Intracellular pH and its regulation in isolated type I carotid body cells of the neonatal rat J. Physiol.
436:107–129, 1991.PubMedGoogle Scholar
Eyzaguirre, C, and J. Lewin. Chemoreceptor activity of the carotid body of the cat. J. Physiol.
159:222–237, 1961PubMedGoogle Scholar
Fitzgerald, R. S., and D. C. Parks. Effect of hypoxia on carotid chemoreceptor response to carbon dioxide in cats. Respir. Physiol. 12
:218–229, 1971.PubMedCrossRefGoogle Scholar
Hornbein, T. F., Z. J. Griffo, and A. Roos. Quantitation of chemoreceptor activity: Interrelation of hypoxia and hypercapnia. J. Neurophysiol.
24:561–568, 1961.PubMedGoogle Scholar
Lahiri, S., and R. G. Delaney. Stimulus interaction in the responses of carotid body single afferent fibers. Respir. Physiol.
24:249–266, 1975.PubMedCrossRefGoogle Scholar
Shirahata, M., S. Andronikou, and S. Lahiri. Differential effects of oligomycin on carotid chemoreceptor responses to O2
in the cat. J. Appl. Physiol.
63:2084–2092, 1987.PubMedGoogle Scholar
Shirahata, M., and R. S. Fitzgerald. The presence of CO2
is essential for hypoxic chemotransduction in the in vivo perfused carotid body. Brain Research
545:297–300, 1991.PubMedCrossRefGoogle Scholar
Shirahata, M., and R. S. Fitzgerald. Dependency of hypoxic chemotransduction in cat carotid body on voltage-gated calcium channels. J. Appl. Physiol.
71:1062–1069, 1991.PubMedGoogle Scholar
Thomas, R. C. Experimental displacement of intracellular pH and the mechanism of its subsequent recovery. J. Physiol.
354:3P–22P, 1984.PubMedGoogle Scholar
© Springer Science+Business Media New York 1992