Abstract:
Relaxation
responses
to samorin
(Isometamidiumchloride)
were.tested on rat aortic
rings pre-contracted
with 10·
7
M noradrenaline
(NA) and SOmMpotassium
chloride
(IcCI).
.
Samorin
(10-8 to IO-4M) relaxedaortic ringspre-contracted
With10·7Mnoradrenaline
concentration
- dependently
but had no effect on' KCI contracted
rings.
A mean
relaxation
of 69.7
±
8.8% was achieved
at a concentration
064
x
iO,sM samorin
with
ECsoof 10.9
±
2.39 x 10~.
.
This relaxation
response
was significantly
attenuated
by removal
of endothelium.
since endothelium
denuded
ring showed
a mean relaxation
of 35
±
8.5% at the same
concentration
of 4 x lO,
s
M samorin
with ECso of 37.4
±
13.7, x 10-6
M
(P<O.OS).
Moreover.
endothelium
intact rings which were pretreated
with 1O~ methylene
blue
showed
a
significant
attenuated
relaxation
to 4 x 10'
s
samorin
with a mean relaxation
of
18.3
±
2.8%and an ECsoof80
±
14x 10-6 M(P<O.OS).
The results therefore
suggest
that samorin-induced
relaxation
of rat aortic smooth
muscle
occurs by endothelium
dependent
mechanism
which is probably
mediated
throu8h
the release of endothelium
- derived relaxing
factor(EDRF)
