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DEVELOPMENT AND TISSUE PLASTICITY
1Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163; 2Institut National de la Santé et de la Recherche Médicale Unit 36 and College de France, 75005 Paris, France; and 3Department of Pharmacology and Toxicology, and Cardiovascular Research Institute, Universiteit Maastricht, 6200 MD, Maastricht, the Netherlands
Submitted 14 August 2002 ; accepted in final form 16 March 2003
An angiotensin (ANG) receptor homologous to the type 1 receptor (AT1) has been cloned in chickens (cAT1). We investigated whether cAT1 expression in various tissues shows maturation/age-dependent changes. cAT1 mRNA levels detected in
renal glomeruli [in situ hybridization (ISH)] and kidney extract (RT-PCR) are
significantly (P < 0.01) higher in 19-day embryos (EB) than in
chicks (CH, 23 wk) and pullets/cockerels (PL/CK, 1416 wk). The
levels in adrenal glands (concentrated in subcapsular regions) are high in EB
and further increased in CH and PL/CK. cAT1 mRNA is also detectable
in smooth muscle (SM)/adventitia of EB and CH aorta and in the adventitia, but
not SM, from PL/CK aortas. The endothelia from small arteries and arterioles,
but not from aorta, express cAT1 mRNA (ISH). In all age groups, ANG
II induces profound endothelium-dependent relaxation of abdominal aorta,
partly (3747%) inhibitable (P < 0.01) by
N
-nitro-L-arginine methyl ester
(L-NAME, 10-4 M), suggesting the presence of
ANG receptor in endothelium. L-NAME-resistant ANG II relaxation,
examined in a limited number of EB or CH aortas, was reduced by 125 mM
K+ or apamin plus charybdotoxin. The results suggest that
1) cAT1 is present in kidney, adrenal gland, and vascular
endothelium (heterogeneity exists among arteries) of EB, CH, and PL/CK, and in
aortic SM/adventitia of EB/CH but only in adventitia of PL/CK; 2)
levels of cAT1 gene expression change during maturation in a
tissue-specific manner; and 3) ANG II-induced relaxation may be
partly attributable to nitric oxide and potassium channel activation.
angiotensin receptor subtype; angiotensin receptor mRNA; endothelium-dependent relaxation; chick embryo; endothelium-derived relaxation factor; endothelium-derived hyperpolarization factor; potassium channel
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