Abstract
Summary
Silicone rubber tubing (0.020 in. i.d.; 0.037 in. o.d.) was inserted in both horns of New Zealand white female rabbits (8-12 months old) as intrauterine contraceptive devices (IUD). After a short recovery period of 1 week to 10 days, these animals were mated with fertile males and about 10 ml of blood were collected from ear arteries every 2 hr beginning 1 hr postcoitum(pc). Serum 20α-hydroxypregn-4-en-3-one (20α-OH-P) was extracted with ether, isolated, and measured by thin-layer and gas-liquid chromatography. The concentrations of 20α-OH-P in serum from mated animals bearing IUD were compared with those from control animals without IUD. It was found that the highest peak of 20α-OH-P was detected at 1.67 ± 1.03 hr pc in intact animals. These values fell significantly by 3-5 hr and were lowest at 9 hr pc. In the IUD group the highest peak of 20α-OH-P occurred at 4.20 ± 1.10 hr pc and fell to lowest value at 9 hr. The difference of the values between these two groups is significant at p < .005. Although the number of stigmata on the ovary werenot significantly different between these two groups, it is clear that the presence of IUD causes a delay in the postcoital rise in 20α-OH-P in this reflex-ovulating species.
We express our thanks to Dr. Harold R. Behrman for his valuable advice in connection with the analysis of steroids. This investigation was supported by NIH Grant HD-03736, The Ford Foundation, and a grant from The Population Council.
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