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GERHILD VAN HOORN and H.-W. DENKER

Max-Planck-Institut für Immunbiologie, D-78 Freiburg, West Germany

(Received 18th February 1975)

The activity of a leucine-β-naphthylamide-splitting enzyme has been shown histochemically to increase markedly before implantation and to reach a sharp peak at 5-6 days post coitum (p.c.) (Denker, 1969; see also description of unmated and 6 days p.c. stages by Petry et al., 1970). The enzyme has been referred to as 'leucine aminopeptidase'. Recently, however, it has become customary to call this class of enzymes 'amino acid arylamidases' or 'amino acid naphthylamidases', because they exhibit properties which differ from those of classical leucine aminopeptidase (cytosol aminopeptidase, EC 3.4.11.1). Amino acid arylamidases are more related to EC 3.4.11.2, but definitive classification is still lacking (see Patterson et al., 1963; for discussion and recent references see Bergmeyer, 1974; Pearse, 1972; Denker & Stangl, 1974).

In the present study the activity of the enzyme at and between the implantation sites was compared.

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J. A. Mitchell and H.-W. Denker

Summary. Localization of uterine arylamidase activity varied between species: arylamidase was found primarily in the apical aspect of uterine epithelial cells in the rabbit, hamster and non-pregnant rat; only moderate staining was observed in these animals in the endometrial stroma. By contrast, arylamidase localization was primarily stromal in the guinea-pig at all stages studied while the luminal epithelium was devoid of reactivity. In all species, uterine enzyme activity increased before implantation but decreased in the vicinity of the blastocyst once implantation had begun. A generalized increase over the entire length of the uterus was seen during the preimplantation phase in the uterine epithelium of the rabbit and in the endometrial stroma of the guinea-pig. Increase in stromal activity appeared to indicate predecidual transformations which were embryo-dependent (i.e. localized to the implantation site) in the rat, or embryo-independent (i.e. occurring throughout the uterus) in the guinea-pig. A subsequent decrease in enzyme activity occurred in the vicinity of the implanting embryo irrespective of the cell type involved (epithelium in the rabbit, stroma/decidua in the rat and guinea-pig). Since arylamidases of the type studied here are integrated membrane proteins, the uniformity of changes observed in different species may reflect profound changes in membrane properties of endometrial cells as an element of the implantation reaction.

Keywords: uterus; arylamidase; aminopeptidase; implantation; epithelium; stroma

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H-P. Hohn, U. Mootz and H-W. Denker

Summary. Endometrial fragments were explanted from pseudopregnant rabbits 4·5 days after injecting with human chorionic gonadotrophin and were precultured for 2 days in suspension culture in the presence of oestradiol and progesterone equivalent to concentrations in rabbit serum at that stage. Preimplantation blastocysts were obtained at day 6·5 of pregnancy and cultured in the presence or absence of precultured endometrial fragments. Attachment of the trophoblast to the endometrium was prevented by continuous agitation. After 2 and 3 days, specimens were monitored for development in vitro using light and scanning electron microscopy.

Although the development of blastocysts was slower in vitro than in vivo in both groups, development was clearly superior in the presence of precultured synchronous endometrial fragments. In the absence of endometrium, the embryonic anlage appeared disordered, particularly in the caudal region, but in the presence of uterine tissue the blastocysts developed much better. Up to nine somites were differentiated; the neural tube had started to close and the various parts of the brain anlage showed incipient differentiation. Syncytiotrophoblast differentiated in the presence or absence of endometrium in the embryonic and abembryonic hemispheres, but typical patterns were maintained better and cell degeneration was less frequent during co-culture. Although the culture model described here has not been optimized using criteria of blastocyst differentiation, the results suggest that culture of blastocysts with precultured synchronous endometrial fragments is advantageous.

Keywords: blastocyst; endometrium; co-culture; in vitro; rabbit