No abstract

Endothelin-like immunoreactivity was observed in the endothelial lining of umbilical vein and artery as well as in the epithelium of the amniotic membrane. High levels of endothelin-like immunoreactivity (0.4-1.4 pmol g-1) were detected in human amniotic membrane, umbilical vessels and placenta. The concentration of endothelin-like immunoreactivity in the amniotic fluid was much higher (77 pmol l-1) than in umbilical cord plasma (10 pmol l-1). Characterization by reverse phase HPLC revealed that most of the endothelin-like immunoreactivity eluted in the position of synthetic endothelin-1 or oxidized endothelin-1. Specific, high affinity binding sites for endothelin-1 were present in placenta and umbilical artery. Endothelin binding sites were also found in cultured smooth muscle cells from the umbilical artery and vein. In the placenta, endothelin-1 and -3 were almost equipotent as competing ligands for endothelin-1 binding sites, whereas in the umbilical artery endothelin-3 was much less potent than endothelin-1. Scatchard analysis of the binding for placental membranes displayed a straight line (r = -0.994) indicating a single class of endothelin receptors with a Kd-value of 80 pmol l-1 and Bmax of 113 fmol mg-1. Endothelin-1 caused potent contractions of umbilical arteries and veins with threshold effects at 10 pmol l-1 while endothelin-3 had no contractile effect up to 10(-7) mol l-1. It is concluded that endothelin-1 predominates over other endothelins in umbilical vessels, amnion and placenta, and high levels of endothelin-1 was observed in foetal circulation and amniotic fluid. Endothelin-receptors seem to be of different types in placenta (ETB type) and umbilical vessels (ETA type).

Endothelialization of prosthetic vascular grafts has been shown to increase patency. We studied the adhesion of cultured endothelial cells of adult human saphenous vein to serum protein coating on expanded polytetrafluoroethylene vascular grafts. The adhesion was compared with that on native or collagen type I-coated grafts. Scanning electron microscopy was used to analyze the precoating and the appearance of the added cultured cells. Presence of radioactively labeled saphenous vein endothelial cells was compared between precoated and uncoated grafts before and after exposure to pulsatile plasma flow. The adherence of saphenous vein endothelial cells was markedly increased on grafts coated with serum proteins or collagen. On both graft types the cells formed confluent areas, which were also present after the plasma flow. The technique was designed to promote endothelialization, using autologous serum as the main source for both growth stimulation during culture and adherence of endothelial cells to grafts. The method may be clinically useful for precoating and endothelialization of vascular grafts.

The findings emphasise the important effect of the matrix on endothelial secretion of PGI2, tPA and PAI-1. Differences in patency after implantation of in vitro endothelialized grafts, may be due to cellular function depending on the types of graft and matrix chosen.

The growth of endothelial cells from small segments of human great saphenous vein was investigated for possible functional studies of endothelial cell properties and endothelialization of cardiovascular prosthetic graft materials. Growth in medium containing fetal calf serum or human serum was compared, and the effects of adding compounds that increase intracellular cyclic adenosine monophosphate levels, that is, cholera toxin and isobutylmethylxanthine, were also examined. It was shown that human serum was more efficient in stimulating cell growth than fetal calf serum at all concentrations tested. It was also shown that the addition of cholera toxin and isobutylmethylxanthine significantly potentiated growth. Minimal Essential Medium with the addition of 40% human serum and cholera toxin (1 umol/L) and isobntylmethylxanthine (33 llmol/L) was shown to be optimal. From a single segment (3 to 5 cm), 20 x 106 human saphenous vein endothelial cells corresponding to 2000 cm 2 or more could be achieved after 3 to 4 weeks in culture. The human saphenous vein endothelial cell cultures retained their cobblestone appearance, expression of von Willebrand Factor (vWF)-antigen, and capacity for prostacyclin production after six passages. We suggest that this provides a practically useful method for studies of cultured endothelium and possibly for preendothelialization of cardiovascular prosthetic materials.