Endothelin receptors in rat pituitary gland

1, We used the quantitative receptor autoradiographic method plus I-125-endothelin-1 (I-125-ET-1), BQ-123, a specific antagonist for the endothelin ET(A) receptor, and sarafotoxin S6c, a selective agonist for the ET(B) receptor to investigate the ET receptor in the rat pituitary gland, 2, The method revealed that the BQ-123-sensitive ET(A) receptor was present predominantly in the anterior lobe and Rathke's pouch, 3, The posterior lobe contained BQ-123-sensitive ET(A) and sarafotoxin S6c-sensitive ET(B) receptors, in almost the same proportion. There was no significant I-125-ET-1 binding to the intermediate lobe. 4. Knowledge of the heterogeneous distribution of ET receptor subtypes in the pituitary gland supplies information that will be pertinent to physiological investigations of the gland.