Stroke, Vol 15, 503-510, Copyright © 1984 by American Heart Association
S Fujiwara and H Kuriyama
The hemolysate (10(-5)-10(-2) times dilution; original hemoglobin
concentration was 0.83 +/- 0.10 X 10(-3)M) evoked the contraction in a dose
dependent manner, and this contraction was composed of low and high
sensitive responses as estimated from the Eadie-Hofstee's plot.
Indomethacin (10(-7)-10(-5)M) inhibited the latter component in the
hemolysate-induced contraction. The membrane potential of smooth muscle
cells was -50 mV and the cell was electrically quiescent. The hemolysate
(greater than 10(-2) times dilution) depolarized the membrane and increased
the ionic conductance of membrane. In rare occasions, the spike potential
was triggered on the hemolysate-induced depolarization. The hemolysate
(10(-5)-3 X 10(-3) times dilution) produced the contraction with no change
in the membrane property. Carbocyclic thromboxane A2 ( cTXA2 ; 2.8 X
10(-10)M) produced the contraction without depolarization of the membrane,
yet the TXA2 synthesis inhibitor, OKY-1581 (10(-5)M), had no effect on the
hemolysate-induced contraction. PGE1, PGE2 and PGF2 alpha (2.8 X 10(- 6)M)
produced the contraction with no change in the membrane property. The
contraction evoked by 2.8 X 10(-6)M PGF2 alpha corresponded well with that
evoked by 3 X 10(-3) times dilution of the hemolysate. Removal of the
endothelium by mechanical rubbing modified the hemolysate-induced
contraction. Under the assumption that OKY-1581 is a selective inhibitor
for TXA2 synthesis, the major part of the contraction (the indomethacin
sensitive component) of the basilar artery is postulated to be due to
synthesis of the primary PG rather than TXA2 by the hemolysate, yet the
hemolysate itself, has to some extent a direct action in evoking the small
contraction.
ARTICLES
Hemolysate-induced contraction in smooth muscle cells of the guinea pig basilar artery
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