In vivo exposure to carbon disulfide increases the contraction frequency of pregnant rat uteri through an indirect pathway

Exposure to CS₂, an organic solvent, is associated with an increased rate of abnormal labor or dysmenorrhea. Contraction of quiescent uteri during pregnancy can cause pre-term labor. We wish to know the effects of in vivo and in vitro exposures to CS₂ on uterine contractions of mid-gestation rats. After 10-d exposure to 300 or 600 mg/kg CS₂, uteri of pregnant rats were measured for contractile responses to various stimuli, such as KCl, oxytocin, carbachol or A23187, a calcium ionophore, using standard muscle bath apparatus. CS₂ treatment significantly increased the contractile response to KCl, carbachol, and A23187. The increase to A23187 was the greatest. In contrast, in vitro exposure to CS₂ immediately suppressed carbachol-induced contraction but did not affect spontaneous and KCl-induced contractions. Results showed the pregnant uterus of the rat is susceptible to CS₂. The influence of in vivo exposure to CS₂ on uterine contraction was opposite to that in vitro. The increased response of CS₂-treated uteri to A23187 suggests that in vivo exposure to CS₂ may sensitize contraction machinery to calcium through indirect pathways.