In vitro effects of anthraquinones on rat intestine and uterus.

Isolated uterus and colon segments were taken from sennoside-pretreated female rats. They indicate a possible decrease in spontaneous contractility of both organ segments. Addition of rhein-Na, as one of the probable active metabolites of sennosides, into the bath medium of isolated colon and ileum segments of untreated rats showed a reduction in contractility at concentrations of more than 10(-5) and 10(-4) mol/l, respectively. Though rhein-Na in concentrations of more than 10(-4) mol/l impaired acetylcholine-mediated contractures of isolated colon, the antagonism was obviously partial and noncompetitive. Isolated uteri from previously estrogen-treated rats did not show a change in the contractile behaviour up to concentrations of 10(-4) mol/l rhein-Na, whereas higher concentrations induced an increase in contractions. The importance of this finding is not clear.