[Role of endothelial nitric oxide synthases in the contractile response to angiotensin II of the aorta in rats. Wistar Kyoto and hypertensive rats].
Dysfunctions of EDRF/L-arginine-NO pathway have been demonstrated in genetic and experimental hypertension. NO is produced through the conversion of L-arginine to L-citruline by NO synthases (NOS) which exist at least in two isoforms. The first termed constitutive (NOSc) and located in the endothelium of the vascular wall results in the basal and stimulated NO production. The second termed inducible (NOSi), which produces large amounts of NO, can be expressed in both smooth muscle and endothelial cells. The aim of the study was to examine and compare in isolated aortic rings of WKY and SHR rats, the activity of the two isoforms of endothelial NO synthases and their influence on the constrictor response induced by angiotensin II. On phenylephrine preconstricted endothelium intact aortic rings (10(-6) M, WKY = 1.2 +/- 0.04 g; SHR = 1.2 +/- 0.07 g; n = 7), carbachol (10(-5) M) induced a greater relaxation in WKY (84 +/- 2.5%) than in SHR (63 +/- 8.5%) rat. This suggests the presence of a low NOSc stimulated activity in the hypertensive strain. When the incubation period was limited to 30 min after equilibration period, L-arginine (3.10(-4) M) did not induce relaxation. When the incubation period was prolonged (180 min), L-arginine induced a relaxation (WKY = 75 +/- 8%; SHR = 58 +/- 10%; n = 7). This relaxation was not observed in a medium containing actinomycin D (10(-6) M) or after endothelium removal, indicating the induction of an endothelial NOSi in the two strains.(ABSTRACT TRUNCATED AT 250 WORDS)
Zerrouk
A
A
Institut Henri Beaufour Research Labs, Les Ulis.
Auguet
M
M
Chabrier
P E
PE
Braquet
P
P
D000594:Amino Acid Oxidoreductases / Q000502:physiology*; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000187:drug effects*; D004730:Endothelium, Vascular / Q000201:enzymology*; D006973:Hypertension / Q000503:physiopathology; D008297:Male; D019001:Nitric Oxide Synthase; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D014661:Vasoconstriction / Q000187:drug effects
D000804:Angiotensin II; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases