AJP - Lung Cellular and Molecular Physiology, Vol 268, Issue 3 424-L431, Copyright © 1995 by American Physiological Society
Specific binding of endothelin-1 to canine tracheal epithelial cells in culture
H. Ninomiya, X. Y. Yu, Y. Uchida, S. Hasegawa and E. W. Spannhake
Department of Environmental Health Sciences, Johns Hopkins School of Hygiene and Public Health, Baltimore, Maryland 21205.
We have studied the binding of endothelin-1 (ET-1) to cultured canine
tracheal epithelial cells. A single specific binding site for 125I-labeled
ET-1 was identified with an apparent dissociation constant (Kd) of 0.2 nM,
maximal binding sites (Bmax) of 6.7 x 10(3) sites/cell, and half-maximal
inhibition (IC50) of 0.3 nM during a 2-h incubation period. The binding of
125I-ET-1 to these cells was inhibited by the presence of unlabeled ET-1,
ET-2, or BQ-123, whereas ET-3 and sarafotoxin S6c did not compete for this
binding site. These binding characteristics are consistent with those of
the ETA receptor. At 37 degrees C, specific binding continuously increased
over 18 h, while at 4 degrees C, it reached a plateau by 2 h. The increase
in binding at 37 degrees C was not associated with DNA synthesis but was
dependent upon protein synthesis, suggesting that epithelial binding sites
were produced continuously under these incubation conditions. Our results
indicate that canine tracheal epithelial cells possess specific binding
sites for ET-1 with characteristics similar to those of the ETA receptor
subtype. Because these cells are demonstrated to both release and bind
ET-1, the results further suggest that ET-1 is involved in paracrine and/or
autocrine control mechanisms in the airway epithelium.
