The effects of herbal oxytocics on the isolated "stripped" myometrium model

Decoctions of Agapanthus africanus and Clivia miniata are used as oxytocic agents in South African traditional herbal medicine. Aqueous extracts of A. africanus and C. miniata leaves have been shown to possess similar uteroto nic activities in the isolated whole uterus preparation. The uterus however , comprises a myometrial and an endometrial layer and the activity of both oxytocin and the prostaglandins differs in these layers. The aim of this st udy was to determine the uterotonic activity of the herbal remedies in an e ndometrium-free preparation (i.e. "stripped" myometrium) and, if active, wh ether this effect could be related to prostaglandin synthesis or to interac tion with specific receptors. The effects of the herbal extracts were teste d on the isolated "stripped" rat myometrium preparation. Both herbal extrac ts caused a direct contractile response by the isolated tissue. Pretreatmen t of the my ometrium with either plant extract augmented the initial respon se to acetylcholine. Preincubation with atropine inhibited the response to cumulative dosage of Agapanthus extract but had no effect on the response t o Clivia. Indomethacin administration did not affect the response of the my ometrium to cumulative dosage of acetylcholine, oxytocin or Clivia extract but inhibited the response to Agapanthus extract. These results clearly ind icate that the Agapanthus and Clivia herbal extracts exhibited uterotonic a ctivity in this model. The study illustrates that the "stripped" myometrium model has successfully differentiated between the mechanisms of action of two herbal oxytocics compared to the whole uterus preparation where their u terotonic activity was thought to be similar. (C) 2000 Elsevier Science Inc . All rights reserved.