A single subcutaneous injection of 1.25mg TP was given to female rats on day 8 or 10. The animals were ovariectomized as adults and tested for deciduoma formation following endometrial traumatization, under an appropriate hormone supply. The uterine response was significantly smaller in size in the rats injected with TP on day 8 than those treated on day 10 in which the response was of the same magnitude as that in the controls receiving no TP. Since the rats treated with TP on day 5 invariably failed to form deciduomata in response to uterine trauma (Takewaki and Ohta, 1974), it is evident that the uterine responsiveness is reduced if the rat is given a single dose of 1.25mg TP approximately within 8 days after birth. Within the critical period, the later the TP treatment, the less drastic are the effects.
If rats were ovariectomized prior to treatment with TP, a single injection of 1.25mg TP on day 10, whether given alone or in combination with subsequent injections of 0.1μg ED for 30 days, could not bring about any alteration of the uterine responsiveness, unlike in those ovariectomized on day 4 and treated with TP on day 5.
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