| Abstract
| - The aim of this research was to study the effect of exogenous interleukin (IL)-8, IL-1 and IL-8 + IL-1 on uterine contractions in rabbits. Four equal groups of non-pregnant rabbits (n = 24) were investigated using either placebo or experimental drugs in the form of vaginal suppositories. The suppositories contained human recombinant IL-8 (200 ng), IL-1 (200 ng), IL-8 (200 ng) + IL-1 (200 ng) or vehicle (Witepsol base, 500 μl). Subsequently, the plasma concentration of prostaglandin (PG) E2 was estimated 3 h after the last dose of treatment. Neutrophil infiltration in the endometrial tissue was studied with anti-rabbit RT2 staining. Suppositories with IL-1 and IL-8 + IL-1 produced contractile responses with increased frequency (P< 0.003, P< 0.0005) and amplitude (P< 0.0001) in vivo, compared with vehicle. IL-1 and IL-8 + IL-1 also caused similar contractile effects with increased frequency (P< 0.01, P< 0.0007) and amplitude (P< 0.0001) in an in-vitro experiment than vehicle. The frequency and amplitude of uterine contractions were more significant with IL-8 + IL-1 than that of IL-1, both in vivo (P< 0.002, P< 0.05) and in vitro (P< 0.005, P< 0.01). IL-8 did not induce any contractions. Prostaglandin concentration was increased ~8-fold with IL-8 + IL-1 (P< 0.0001) and 2.5-fold with IL-1 treatment (P< 0.0001). Neutrophil numbers were significantly increased with IL-8 + IL-1 > IL-8 > IL-1 (P< 0.002, P< 0.0003 and P< 0.008) compared with vehicle. Our data suggest that IL-8 stimulates IL-1-induced uterine contractions through PGE2 production and could be an important process during labour and delivery.
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