In 1919 Obata1 of the University of Tokyo showed that salt solution extracts of the human placenta are highly toxic for rabbits and mice. Within the limits of the experimental error extracts from the normal human placenta and from the placentas of eclamptic patients were identical in toxicity. He found that normal human serum can neutralize the placental toxin but that the antitoxic titer is low in eclamptic women. He concluded that eclampsia is an intoxication by the placental toxin made possible by a weakened antitoxic capacity of the maternal blood. The cause of this reduction of maternal antitoxin was not determined. His associates2 found that a similar toxic product was produced by autolysis of the uterus.
Interest in Obata's toxic theory has been revived by Krichesky,3 who recently discovered that saline extracts of pregnant and pseudopregnant rabbit uteri are highly toxic when injected intravenously into rabbits.
ENDOMETRIAL TOXIN. JAMA. 1947;134(4):367. doi:10.1001/jama.1947.02880210045012
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