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The effects of hypercapnic acidosis and hypoxia on intracellular Ca(2+) concentration ([Ca(2+)](i)) were determined with Indo 1 in enzymatically isolated single type I cells from neonatal rat carotid bodies. Type I cells responded to graded hypoxic stimuli with graded [Ca(2+)](i) rises. The percentage of cells responding was also dependent on the severity of the hypoxic stimulus. Raising CO(2) from 5 to 10 or 20% elicited a significant increase in [Ca(2+)](i) in the same cells as those that responded to hypoxia. Thus both stimuli can be sensed by each individual cell. When combinations of hypoxic and acidic stimuli were given simultaneously, the responses were invariably greater than the response to either stimulus given alone. Indeed, in most cases, the response to hypercapnia was slightly potentiated by hypoxia. These data provide the first evidence that the classic synergy between hypoxic and hypercapnic stimuli observed in the intact carotid body may, in part, be an inherent property of the type I cell.

Type

Journal article

Journal

Am J Physiol Lung Cell Mol Physiol

Publication Date

07/2000

Volume

279

Pages

L36 - L42

Keywords

Acidosis, Animals, Calcium, Calcium Signaling, Carotid Body, Chemoreceptor Cells, Hypercapnia, Hypoxia, Intracellular Membranes, Osmolar Concentration, Rats, Rats, Sprague-Dawley