Identification of vasopressor constituents of amniotic fluid in pregnancy toxaemia

Summary The vasopressor activity of human amniotic fluid was assessed in 46 primigravidas during the third trimester of pregnancy. The subjects included 20 normal and 26 cases of pregnancy toxaemia. For identification of the vasoptessor activity of the amniotic fluid, blood pressure measurements were made in the intact rat, and the smooth muscle contraction of the rat ascending colon preparation was determinedin vitro. The samples of amniotic fluid showing vasoptessor activity were lyophilized and subjected to gel filtration using Sephadex G-100. The various fractions thus obtained were monitored at 280 nm and the pressor activity was re-estimated. It was observed that most of the pressor activity of the amniotic fluid of the toxaemic patients was capable of causing contraction of the rat colon as well as a significant rise in the systolic blood pressure of the intact rat. Furthermore, this activity was found to be heat-labile and was completely blocked by cinnarizine. Fractionation of the amniotic fluid showing vasopressor activity by gel filtration further substantiated the findings reported above. On the basis of these results it was concluded that the pressor activity of the amniotic fluid was due to the presence of an angiotensin II-like substance. Its concentration was found to be higher in the toxaemic group than in normotensive subjects.