MODULATION of PROSTACYCLIN PRODUCTION BY HUMAN UMBILICAL VEIN ENDOTHELIAL CELLS WITH ECGF/HEPARIN MEDIUM : ROLE OF CELLULAR DENSITY AT CONFLUENCE

Prostacyclin (PGI2) is a major product of arachidonic acid metabolism in vascular endothelial cells. In addition to the role of exogenous agents, its production could be modulated by culture conditions : proliferative state, medium renewal, subcultivation... The use of endothelial cell growth factor (ECGF) associated with heparin has been shown to improve human endothelial cell proliferation. Here we report that human umbilical vein endothelial cells (HUVEC) grown in that medium produce less prostacyclin than without growth factor.HUVEC were cultured in RPMI-199 1:1 + 20% fetal calf serum, added or not with ECGF (Bovine hypothalamus extract BTI Cambridge, 24 ug/ml) and heparin (from porcine intestinal mucosa, Signa, 90 ug/ml). After 4 days in culture, medium was removed and replaced by Tyrode Hepes buffer and basal production was measured after 20 min. Cells were then submitted to 5 min thrombin to assess PGI2 production in stimulated conditions. PGI2 production was estimated by specific radioimmunoassay for 6 keto PGFjalpha. For each point, cell number in the culture was counted after Trypsin EDTA treatment. In the present study, cells grown in ECGF-heparin medium produce lower amount of PGI2, compared to heparin or control medium. This result was observed in both basal and stimulated conditions. For each medium (ECGF-heparin, heparin, control), correlations between PGI2 production per cell and log cell density were shown to be significantly negative.These observations suggest that ECGF effect on PGI2 production could be a consequence of its growth factor activity, notably by the fact that it leads to an endothelial monolayer made of more numerous cells. Since it is now suggested by a number of clinical observations that PGI2 is rather produced in pathological conditions, culture models showing a weak production of PGI2 appear in that connection doser to the physiological conditions.