Angiotensin receptors expressed in adrenocortical y-1 cells.
Tian, Ying, Albert J. Baukal, Kathryn Sandberg, Kenneth E. Bernstein,
Tamas Balla, and Kevin J. Catt.
Endocrinology and Reproduction Research Branch, National Institutes
of Health, Bethesda, MD 20892 and Department of Pathology, Department
of Medicine, Emory University School of Medicine, Atlanta, GA
30322
APStracts 2:0259E, 1995.
Adrenocortical Y-1 cells were stably transfected with the AT1a and
AT1b subtypes of the rat angiotensin II (Ang II) AT1 receptor cDNA to
study the pharmacological and functional properties of the two
receptors. Selected clones of transfected cells expressing either of
the two receptor subtypes bound the native ligand, Ang II, and the
peptide antagonist [Sar1, Ile8]Ang II, with similar affinities but
they differed in their relative affinities for the non-peptide
antagonist losartan (IC50 9.7 and 4.7 nM), Ang III (126 and 33 nM)
and the peptide antagonist [Sar1,Gly8]Ang II (6.2 and 1.2 nM).
Photoaffinity labeling of the expressed receptors revealed a single
component of 65 kDa for both receptor subtypes, suggesting that both
receptors were glycosylated in a similar manner. The sensitivity of
125I-Ang II binding to AT1a and AT1b receptors to guanine nucleotides
was unaffected by pertussis toxin treatment. Ang II stimulated the
formation of inositol phosphates and increased the level of
cytoplasmic Ca2+ in both AT1a-and AT1b-transfected Y-1 cells.
However, Ang II had little effect on forskolin-induced cAMP
accumulation, causing only minor inhibition in AT1a- and slight
enhancement in AT1b-transfected cells. These data indicate that AT1a
and AT1b receptors show small but significant differences in their
binding pharmacology, and upon activation are coupled through Gq/G11
to the phosphoinositide-Ca2+ signaling pathway. However, neither AT1a
nor AT1b receptors exhibit coupling to Gi and inhibition of adenylate
cyclase when expressed in murine adrenal tumor cells.
Received 30 May 1995; accepted in final form 6 December 1995.
APS Manuscript Number E235-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 December 95