Discrimination between the functional and biochemical effects of two herbal oxytocics on the rat myometrium

This study on the rat myometrium is the first report where the effects of h erbal extracts used as oxytocics in traditional medicine have been systemat ically analysed in the same preparation at the level of functional (contrac tile) and biochemical (second messenger generation) responses. Extracts of Agapanthus africanus and Clivia, miniata (used in South African traditional medicine) were compared with other uterotonic agents with regard to their ability to stimulate phosphoinositide metabolism in the rat myometriurn and cause accumulation of [H-3]inositol phosphates. The maximal contractile re sponse of the isolated rat myometrium in response to stimulation by the her bal extracts and agonists was compared with the maximal contractile respons e to cumulative addition of acetylcholine. The rank order of intensity of s timulation of [H-3]inositol phosphate generation was: oxytocin > Agapanthus > prostaglandin F(2)alpha (PGF(2 alpha)) > serotonin > acetylcholine > Cli via > ergometrine. This differed from the rank order of maximum contractile response: oxytocin > acetylcholine > PGF(2 alpha) > serotonin approximate to Clivia > Agapanthus > ergometrine. Activity was also identified in chemi cal fractions of the plants and components common to both plants have been identified in the isolated active fractions. These results have identified that the uterotonic activity of Agapanthus is linked to increased turnover of phosphoinositides as a signal transduction mechanism, whereas this appea rs to play a less significant role in the uterotonic activity of Clivia. Th is study illustrates the benefits of using the measurement of stimulation o f phosphoinositide metabolism as a bioassay in phytomedical research.