Distribution of epithelioid cells in the wall of the chicken aorta and their functional role as chemoreceptors.
BACKGROUND
The ultrastructural characteristics of epithelioid cells in the wall of the chicken aorta have been studied by several investigators. Their characteristics were homologous to those of carotid body type I cells and are considered to be one of the peripheral chemoreceptors. However, there are few descriptions about their location, distribution, and how they react to chemical signals, nor have there been many reports about the localization of bioactive substances in the epithelioid cells. Therefore we designed this investigation to address these problems.


METHODS
Wholemount immunohistochemistry using antiserotonin antiserum, scanning (SEM), and transmission (TEM) electron microscopy were used to observe the epithelioid cells and the lumen of the chicken aorta. The localizations of bioactive substances in the epithelioid cells were immunohistochemically investigated using 11 antisera.


RESULTS
Epithelioid cells were dispersed in the wall of the aorta, forming a band approximately 1 mm in width, located 10 mm proximal to the confluence of the right and left ligamenta arteriosa. Serotonin, chromogranin, and neuron specific enolase immunoreactivities were detected in the epithelioid cells. SEM observations clearly demonstrated intraendothelial fenestrations, 1-3 microns in diameter, on the endothelial surface of the region of the band of epithelioid cells. TEM observations revealed that these fenestrations corresponded to endothelial gaps, directly beneath which epithelioid cells were sometimes located.


CONCLUSIONS
The epithelioid cells are in direct access to the aortic lumen through endothelial fenestrations. Thus they may be able to perceive chemical signals from arterial blood directly.
Miyoshi
M
M
Department of Veterinary Anatomy, Faculty of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
Hashimoto
Y
Y
Kon
Y
Y
Sugimura
M
M
D000818:Animals; D001011:Aorta / Q000166:cytology*; D002628:Chemoreceptor Cells / Q000502:physiology*; D002645:Chickens; D002864:Chromogranins / Q000032:analysis; D015622:Epithelioid Cells / Q000737:chemistry / Q000648:ultrastructure*; D005260:Female; D007150:Immunohistochemistry; D008297:Male; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D010751:Phosphopyruvate Hydratase / Q000032:analysis; D012701:Serotonin / Q000032:analysis
D002864:Chromogranins; D012701:Serotonin; D010751:Phosphopyruvate Hydratase