Determination of the Sensitive Period for the Induction of Deciduomata in the Rat by Different Inducing Procedures

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Abstract
A number of nonspecific inducers, including distilled water, saline, Hank's solution, trypsin, bradykinin, histamine and others, when injected intraluminally into the rat uterus on Day 4 of pseudopregnancy are capable of stimulating extensive deciduoma formation if the timing of the injection is controlled. Optimal time is around 4.5 days after ovulation, i.e., between 11:00 AM and 1:00 PM on Day 4. No response is obtained following an injection on Day 3 or 5 of pseudopregnancy. Intraperitoneal administration of pyrathiazine was not very effective as a deciduoma inducer in this strain of rat. While the knifescratch method for deciduoma induction is most useful, particularly because of its longer duration of action, results obtained with the intraluminal injection method better correlate, on a temporal and histologic basis, with decidua induction by means of the rat embryo. A hypothesis is advanced to account for the development of deciduomata either in a nodular form or as a massive growth occupying an entire uterine cornu. This is based on 2 variables, each of which is time-dependdent. These are: a) the duration of maximal uterine sensitivity and b) the duration of action (specifically, the half-life) of the inducing stimulus. Synchronization of these 2 variables produces the massive growth, while asynchronization produces nodules.