Novel angiotensin receptor subtypes in fowl.
We reported previously that blood vessels of domestic fowl contain angiotensin (ANG) receptors on 1) endothelium, mediating vasorelaxation via endothelium-derived relaxing factor and guanosine 3',5'-cyclic monophosphate; 2) vascular smooth muscles, mediating neither relaxation nor contraction; and 3) presumably adrenergic nerve endings, transmitting vasopressor action via a release of norepinephrine. We aimed in the present study to determine fowl vascular ANG receptor subtypes and relate them to function. [Val5]ANG II (native fowl ANG II) increased mean arterial pressure of anesthetized, ganglion-blocker-treated fowl. The dose-pressor response curve for fowl ANG II was not altered by pretreatment (i.v.) with the ANG receptor subtype 1 (AT1) antagonist Dup-753 (losartan, 10 mg/kg) or the subtype 2 (AT2) antagonist PD-123319 (10 mg/kg). Furthermore, cumulative doses (1-20 mg/kg) of losartan or PD-123319 did not selectively inhibit ANG II-induced pressor responses. In reserpine- and prazosin-treated anesthetized fowl, [Val5]ANG II caused dose-dependent vasodepressor actions inhibited by neither losartan (10 mg/kg) nor PD-123319 (10 mg/kg). Likewise, [Val5]ANG II-induced vasorelaxation of fowl aortic rings in vitro was not inhibitable by PD-123319 or losartan (10(-5) M). Specific binding of 125I-labeled ANG II to the aortic endothelium was markedly displaced by ANG II, but not selectively by PD-123319 or losartan. Specific binding of 125I-ANG II ligand to the membrane fraction of aortic smooth muscles was displaced (50% inhibitory concentration) by [Val5]ANG II (3.3 x 10(-8) M) and slightly by PD-123319 (3.7 x 10(-5) M), but not by losartan or EXP-3174, an active metabolite of losartan.(ABSTRACT TRUNCATED AT 250 WORDS)
Nishimura
H
H
Department of Physiology and Biophysics, University of Tennessee, Memphis 38163.
Walker
O E
OE
Patton
C M
CM
Madison
A B
AB
Chiu
A T
AT
Keiser
J
J
D000109:Acetylcholine / Q000494:pharmacology; D000804:Angiotensin II / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D001012:Aorta, Abdominal / Q000187:drug effects / Q000502:physiology*; D001713:Biphenyl Compounds / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects*; D002462:Cell Membrane / Q000378:metabolism; D002645:Chickens / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000378:metabolism*; D005260:Female; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D019808:Losartan; D008955:Models, Cardiovascular; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D011725:Pyridines / Q000494:pharmacology; D011945:Receptors, Angiotensin / Q000145:classification / Q000502:physiology*; D012110:Reserpine / Q000494:pharmacology; D013777:Tetrazoles / Q000494:pharmacology
D057911:Angiotensin Receptor Antagonists; D001713:Biphenyl Compounds; D007093:Imidazoles; D011725:Pyridines; D011945:Receptors, Angiotensin; D013777:Tetrazoles; D000804:Angiotensin II; C073402:PD 123319; D012110:Reserpine; C066026:losartan carboxylic acid; D019808:Losartan; D000109:Acetylcholine