Regulation of Intracellular pH in Type I Cells of the Neonatal Rat Carotid Body

Abstract

Although the carotid body is the principal arterial pH receptor, little is known about its ionic mechanisms for pH-detection. A prime candidate for the H⁺ chemo sensory element is the type I (glomus) cell, also believed to be the site of O₂-chemoreception. This cell contains a rich variety of neuroactive compounds, most notably catecholamines, which are secreted in response to extracellular acid/base challenges and to hypoxia (Fidone & Gonzalez, 1986). In this way, local endings of the carotid sinus nerve are believed to be elicited. Indirect evidence has suggested that, in order to get chemoreception of extracellular acidosis/alkalosis there must first be a change of intracellular pH in the type I cell (Hanson, Nye & Torrance, 1981; Rigual, Lopez-Lopez Gonzalez, 1991). Until recently, however, there was no accurate way of directly measuring pH in this cell. Consequently, it was not known if pH, was regulated by acid equivalent efflux and influx mechanisms as it is in many other cells (Roos & Boron, 1981; Thomas, 1984 & Vaughan-Jones, 1988). In the present work we have therefore used the intracellular fluorescent probe SNARF-1 to examine intracellular pH and its regulation in type I cells isolated enzymically from the neonatal rat carotid body.