Distribution of uteroglobin in the rabbit endometrium after treatment with an anti-progesterone (ZK 98.734): an immunocytochemical study.

The effect of the synthetic steroid ZK 98.734, an anti-progesterone with high affinity for the progesterone receptor, on uteroglobin distribution in the rabbit endometrium has been studied by means of immunocytochemistry. Rabbits were treated with ZK 98.734 during the second, third and fourth day of pseudopregnancy. From the fifth up to the eighth day of pseudopregnancy the uteri were processed for immunocytochemistry using the peroxidase--antiperoxidase (PAP) and protein A--gold techniques. Uteroglobin synthesis and release could be inhibited by the anti-progesterone treatment. On day 5 and 6 there was no labelling of the uterine secretions and only a few diffusely labelled non-ciliated cells could be seen in the surface and glandular epithelium. The inhibition was reversible in so far as on day 7 and day 8 the rabbit endometrium exhibits a clear labelling of the uterine secretion as well as an increase in positive reaction in the epithelial cells lining the glands. In all treated animals the intracellular uteroglobin labelling was confined to the Golgi complex and secretory vesicles with a significant increase from the fifth to the eighth day of pseudopregnancy. Together with the described morphological changes these results indicate that ZK 98.734 is capable of inducing a delayed secretion in the rabbit endometrium, which is comparable to the delay in secretion caused by post-coital oestradiol treatment. However, the antigestagen effect is probably due to a different mechanism of endocrine interference with pre-implantation. The most exciting consequence, so far, is the prolongation of progesterone action after the anti-progesterone treatment had ended.