Toxicity of Saline Extracts of Rabbit Uterus After Estrogen Administration. ∗

Abstract

In a previous communication it was demonstrated that saline extracts of full term or immediately post-partum rabbit uteri contain a toxic substance lethal to other rabbits when injected intravenously in doses of 6 cc or less. 1 It was also reported that this toxic substance possesses some physiological properties similar to those of histamine. 2

Among the consistent characteristics of a full term or immediately post-partum rabbit uterus containing the toxic substance, there are: (1) increased color, of vascular origin; 3 (2) increased volume of the entire uterus; 4 and (3) increased amounts of intercellular fluid, or edema. 5 Similar uterine changes after administration of estrogens to non-pregnant animals have been adequately demonstrated by several investigators. Moreover, it has been demonstrated, at least in other species, that estrogens are present in both blood and urine in increasing amounts as pregnancy progresses. 6 The presence of high concentrations of estrogens in the final stages of pregnancy, and the similarity of uterine changes at term and after administration of estrogens, suggests the possibility that the primary female hormone may bear some relationship to the presence of a toxic substance in uterine tissues. For these reasons it was considered advisable to determine if the toxic factor can be recovered from uteri of non-pregnant rabbits previously injected with estrogens.

Ten adult non-pregnant rabbits were treated as follows: (1) 4 animals received theelin; (2) 3 received Progynon B; and (3) 3 received stilbesterol. These hormones were given subcutaneously in doses indicated in the table. Forty-eight hours after the last injection the animals were sacrificed, the uteri excised, and extracts prepared as described in an earlier communication, so that one cc of extract represented 0.5 g fresh uterine material. 2 Four non-pregnant untreated animals provided uteri serving as controls.