T. Ge et al., Increased response to prostaglandin H-2 precedes changes in PGH synthase-1expression in the SHR aorta, ACT PHAR SI, 20(12), 1999, pp. 1087-1092
AIM: To determine the expression of PGH synthase-1 and the sensitivity of v
ascular smooth muscle to PGH(2) in the aorta from the SHR at an age when no
endothelium-dependent contractions to acetylcholine are observed under con
trol conditions. METHODS: All experiments were performed in parallel on aor
tas from 20-wk-old SHR and Wistar-Kyoto normotensive rats (WKY). Rings, wit
h or without endothelium, were suspended in conventional organ chambers for
the recording of changes in isometric force. The expression of PGH synthas
e-1 was evaluated by reverse transcription-polymerase chain reaction (RT-PC
R) and Western blot analysis. RESULTS: Under control conditions acetylcholi
ne did not cause contractions of rings with or without endothelium. However
, in the presence of nitro-L-arginine (NLA, an inhibitor of nitric-oxide sy
nthase), it evoked endothelium-dependent contraction in the SHR but not in
the WKY aortas. The expression of PGH synthase-1 was comparable in the aort
as of both strains (with and without endothelium). PGH2 caused greater cont
ractions in rings without endothelium from the SHR than those from WKY, whi
le U46,619 evoked a comparable response, in aortas from both strains. CONCL
USION: In the aorta of 20-wk-old SHR, endothelium-dependent contractions to
acetylcholine are observed only when the production of nitric oxide is pre
vented. They are associated with an augmented sensitivity of the smooth mus
cle to PGH(2), but not with an increased expression of PGH synthase-1.