Effects of Hypoxia on Carotid Body Type I Cells and Their Catecholamines. A Biochemical and Morphologic Study

Abstract

The carotid body of different species contains a high concentration of catecholamines, mainly dopamine and norepinephrine (5,6,8,10,12,16). Electrophysiological studies have shown that these catecholamines may play a role as modulators of the chemoreceptor discharge (2,13,15). The dominating cells, the type I cells, are believed to store the catecholamines in their granulated vesicles. Morphologic studies of these cells and their granulated vesicles during stimulation, e.g., by hypoxia for shorter or longer periods of time, have shown rather conflicting results (1,3,4). In our attempts to further understand the chemosensory mechanisms of carotid body we have focused our interest on the involvement of the carotid body catecholamines, the type I cells, and their granulated vesicles in the receptor machinery during hypoxia. The catecholamine analysis was performed by aid of mass fragmentography. As has been recently shown (8,9), the mass fragmentography technique is extremely suitable to analysis of the catecholamines of the carotid body, where in most species only small amounts of tissue are available. Quantitative electron microscopy or morphometry was used to study the type I cells and their granulated vesicles.