DIFFERENCES OF MICROVASCULAR ENDOTHELIUM IN THE BOVINE CORPUS-LUTEUM OF PREGNANCY AND THE CORPUS-LUTEUM OF THE ESTROUS-CYCLE

The purpose of the present study was to investigate potential modulati ons of endothelial cells of the bovine corpus luteum (CL) during pregn ancy. Luteal endothelia of pregnant and non-pregnant cows were isolate d and purity of cultures was verified by flow cytometric quantificatio n of three independent endothelial markers (von Willebrand factor, ang iotensin converting enzyme, Bandeiraea simplicifolia agglutinin I liga nds). Different cellular parameters including light and electron micro scopical investigation of morphology and growth characteristics as wel l as quantification of cellular lectin binding sites were compared. Ex tensive heterogeneity between luteal endothelial cells in pregnant and non-pregnant animals could be demonstrated, reflected in functional a ttributes like angiogenic activity, ultrastructural characteristics an d the quantitative expression of cellular carbohydrates. Two different morphological types of cells ('cobblestone growth pattern' and 'arcua te growth pattern') were isolated from the CL of pregnancy as well as from the cyclic CL. Spontaneous angiogenic activities, including cellu lar migration in band-like structures and formation of ring-like struc tures, were observed in endothelial cells isolated from the CL of preg nant cows exclusively. This strongly suggests that microvascular lutea l endothelium of pregnant animals, in contrast to the one of non-pregn ant animals, is able to produce quantitatively and/or qualitatively sp ecific angiogenesis factor(s). Heterogeneity between luteal endothelia l cells in the pregnant and non-pregnant animal could also be demonstr ated by quantification of lectin (Bandeiraea simplicifolia agglutinin I, concanavalin A, Dolichos biflorus agglutinin, Ulex europaeus agglut inin I, wheat germ agglutinin) binding sites: quantitative expression of specific endothelial cell surface carbohydrates could be correlated to the status of pregnancy, thus emphasizing the actual need of quant ification of lectin binding.