The role of prostaglandins in the stimulatory action of catecholamines on myometrial activity in term pregnant women.

The response of small strips of human myometrium to catecholamines was investigated using a superfusion technique. In term pregnant uteri, adrenaline (A) and noradrenaline (NA) caused contraction of both the upper and lower segments, but there was no significant change in response depending on whether or not the patient was in labor. Phenoxybenzamine blocked the excitatory effect of both A and NA, suggesting an alpha-adrenoceptor-mediated effect. Propranolol did not enhance the effect of A or NA, indicating that stimulation of beta-adrenoceptors does not contribute to the effect on the pregnant human uterus. Pretreatment of the tissue with indomethacin or eicosa-5,8,11,14-tetraynoic acid (ETA), drugs known to block endogenous prostaglandin synthesis, markedly reduced the effects of both A and NA. This suggests a specific role of prostaglandins in the mechanism of action of catecholamines on the human myometrium.