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 o f abnormal labor or dysmenorrhea. Contraction of quiescent uteri during pre gnancy can cause preterm labor. We wish to know the effects of in vivo and in vitro exposures to CS2 on uterine contractions of mid-gestation rats. Af ter 10-d exposure to 300 or 600 mg/kg CS2, uteri of pregnant rats were meas ured for contractile responses to various stimuli, such as KCl, oxytocin, c arbachol or A23187, a calcium ionophore, using standard muscle bath apparat us. CS2 treatment significantly increased the contractile response to KCI, carbachol, and A23187. The increase to A23187 was the greatest. In contrast , in vitro exposure to CS2 immediately suppressed carbachol-induced contrac tion but did not affect spontaneous and KCI-induced contractions. Results s howed the pregnant uterus of the rat is susceptible to CS2. The influence o f in vivo exposure to CS2 on uterine contraction was opposite to that in vi tro. The increased response of CS2-treated uteri to A23187 suggests that in vivo exposure to CS2 may sensitize contraction machinery to calcium throug h indirect pathways.