Pathways for Calcium Entry into Type I Cells: Significance for the Secretory Response

Abstract

From a biophysical standpoint, data relevant to chemotransduction in the carotid body are difficult to interpret and there is no coherent scheme relating membrane properties of type I cells to the chemoreception process. Thus, while the membrane potential of type I cells has been reported to be independent of extracellular K+ (Baron and Eyzaguirre, 1977), these cells nonetheless exhibit a Ca++-dependent release of dopamine (DA) when exposed to K+-rich media (Almaraz et al., 1985). When challenged by chemoreceptor stimuli (low PO₂ or pH, high PCO₂, drugs, etc.), the membrane properties of these cells (i.e., membrane potential, specific membrane resistance and capacitance) exhibit changes of variable magnitude and direction, with no clear or consistent pattern for any given stimulus (Baron and Eyzaguirre, 1977: Eyzaguirre et al., 1983). Such observations render it difficult to formulate a unified concept of the biophysical aspects of chemotransduction.