DISTRIBUTION OF EPITHELIOID CELLS IN THE WALL OF THE CHICKEN AORTA AND THEIR FUNCTIONAL-ROLE AS CHEMORECEPTORS

Background: The ultrastructural characteristics of epithelioid cells i n the wall of the chicken aorta have been studied by several investiga tors. Their characteristics were homologous to those of carotid body t ype I cells and are considered to be one of the peripheral chemorecept ors. However, there are few descriptions about their location, distrib ution, and how they react to chemical signals, nor have there been man y reports about the localization of bioactive substances in the epithe lioid cells. Therefore we designed this investigation to address these problems. Methods: Wholemount immunohistochemistry using antiserotoni n antiserum, scanning (SEM), and transmission (TEM) electron microscop y were used to observe the epithelioid cells and the lumen of the chic ken aorta. The localizations of bioactive substances in the epithelioi d cells were immunohistochemically investigated using 11 antisera. Res ults: Epithelioid cells were dispersed in the wall of the aorta, formi ng a band similar to 1 mm in width, located 10 mm proximal to the conf luence of the right and left Ligamenta arteriosa. Serotonin, chromogra nin, and neuron specific enolase immunoreactivities were detected in t he epithelioid cells. SEM observations clearly demonstrated intraendot helial fenestrations, 1-3 mu m in diameter, on the endothelial surface of the region of the band of epithelioid cells. TEM observations reve aled that these fenestrations corresponded to endothelial gaps, direct ly beneath which epithelioid cells were sometimes located. Conclusions : The epithelioid cells are in direct access to the aortic lumen throu gh endothelial fenestrations. Thus they may be able to perceive chemic al signals from arterial blood directly. (C) 1995 Wiley-Liss, Inc.