We investigated the gene expression and localization of endothelin-l (
ET-1) receptor subtypes ET(A) and ET(B) in the rat adrenal cortex as w
ell as their involvement in the corticosteroid secretagogue effect of
ET-1 in vitro. Reverse transcription-polymerase chain reaction with pr
imers specific for ET(A) and ET(B) cDNAs demonstrated the expression o
f both receptor genes in homogenates of adrenocortical tissue. However
, in isolated zona glomerulosa and zona fasciculata cells, only ET(B)
mRNA was detected. Autoradiographic examination of the selective displ
acement of I-125-ET-1 binding by BQ-123 and BQ-788 (specific ligands f
or ET(A) and ET(B), respectively) indicated that zona glomerulosa poss
esses both ET(A) and ET(B), whereas zona fasciculata is exclusively pr
ovided with ET(B). ET-1 enhanced in a concentration-dependent manner a
ldosterone and corticosterone secretions of dispersed zona glomerulosa
and zona fasciculata cells, respectively. The ET(B) antagonist BQ-788
markedly reduced the secretory response of zona glomerulosa cells and
completely suppressed that of zona fasciculata cells, whereas the ET(
A) antagonist BQ-123 was ineffective. These findings indicate that in
the rat, the adrenocortical secretagogue action of ET-1 is mediated by
the ETB receptor subtype and that the ET(A) receptor is not directly
involved in such an effect.