Inhibitory effect of barusiban and atosiban on oxytocin-induced contractions of myometrium from preterm and term pregnant women.
BACKGROUND
A synthetic oxytocin analogue, barusiban, was shown to potently inhibit oxytocin-induced activity of myometrium from term pregnant women. The responsiveness to vasopressin was not influenced by the compound.


OBJECTIVE
To test the effect of barusiban and a reference compound, atosiban, on oxytocin-induced activity of myometrium from women at preterm pregnancy in comparison to myometrium from women at term.


METHODS
Fifteen preterm (30-36 gestational weeks) and 12 term pregnant women (38-41 weeks) who underwent cesarean delivery donated myometrial tissue for the study. Concentration-response curves following oxytocin administration to isolated myometrial strips were recorded in control experiments, in the presence of barusiban at concentrations of 2.5, 25, and 250 nM, and of atosiban at concentrations of 25, 250, and 750 nM. Effective concentration 50% (EC50) and pA2 values were calculated.


RESULTS
Both antagonists in higher concentrations increased the EC50 values to oxytocin. The median pA2 value for preterm myometrium with barusiban was 9.76 and with atosiban 7.86. For term myometrium the corresponding pA2 results were 9.89 and 7.81, respectively. None of these pA2 values differed to any statistically significant degree.


CONCLUSIONS
The selective oxytocin antagonist, barusiban, concentration-dependently inhibits oxytocin-induced myometrial contractions of both preterm and term myometrium at least as potently as atosiban. It remains to be determined if the selectivity of barusiban for the oxytocin receptor confers an advantage over atosiban as a tocolytic in preterm labor.
Pierzynski
Piotr
P
Department of Pathophysiology of Pregnancy, Medical University of Bialystok, Bialystok, Poland.
Lemancewicz
Adam
A
Reinheimer
Torsten
T
Akerlund
Mats
M
Laudanski
Tadeusz
T
D000328:Adult; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D009215:Myometrium / Q000187:drug effects* / Q000502:physiology; D010121:Oxytocin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011247:Pregnancy; D047928:Premature Birth / Q000517:prevention & control; D014590:Uterine Contraction / Q000187:drug effects*; D014668:Vasotocin / Q000031:analogs & derivatives* / Q000494:pharmacology*
C047046:atosiban; D010121:Oxytocin; D014668:Vasotocin