OxyFile #222

Potentiating effect of hydrogen peroxide on the serotonin-induced 
vasocontraction in human umbilical artery.

Author:  Watanabe K; Okatani Y; Sagara Y;

Source:  Acta Obstet Gynecol Scand 1996 Oct; 75(9):783-9


BACKGROUND: Our objective was to investigate the role of 
hydrogen peroxide in the vasocontraction induced in the 
human umbilical artery by serotonin. 

METHODS: Umbilical arteries collected from healthy women at term 
were cut helically and suspended in an organ bath to record 
isometric mechanical activity. In Study I, we measured the 
concentration-contraction response to serotonin with or without 
pretreatment with hydrogen peroxide (0.01-10 microM). In Study 2, 
vessels were pre-incubated with L-arginine (0.1-10mM), or with 
hydrogen peroxide (10 mM) and L-arginine (1 mM), then serotonin 
was added cumulatively. In Study 3, vessels were suspended 
in a calcium-free solution containing potassium chloride 
20 mM, and a cumulative concentration-response curve to 
calcium chloride (10(-5)-10(-3) M) was constructed for 
vessels pretreated with hydrogen peroxide (10 microM). 
In Study 4, vessels were pre-treated with M1, an inhibitor 
of 5-HT2 serotoninergic receptors, and hydrogen peroxide 
(10 microM), and then prostaglandin F2 alpha (9.0 x 10(-7) 
M). Finally, we measured the 5-HT1 receptor-mediated relaxation 
induced by serotonin. 

RESULTS: Hydrogen peroxide (1 or 10 microM) significantly 
potentiated the contractile response to serotonin (p < 0.04, p < 
0.005). L-arginine (1 or 10 mM) significantly reduced the 
contractile response to serotonin (p < 0.02, p < 0.0002). 
Pretreatment with L-arginine significantly suppressed the 
potentiating effect of hydrogen peroxide on the serotonin-induced 
contraction. The sensitivity of the arteries to calcium chloride 
in the presence of hydrogen peroxide did not differ from that in 
the control group. Pretreatment with hydrogen peroxide 
significantly reduced the 5-HT1 serotoninergic receptor-mediated 
relaxation at higher concentrations of serotonin (1.23 x 10(-4) M, 
2.47 x 10(-4) M, 2.47 x 10(-4) M). 

CONCLUSION: Hydrogen peroxide potentiated the umbilical artery 
contraction induced by serotonin. This action may be mediated by 
suppression of endogenous nitric oxide activity.