[Characteristics of the spontaneously transformed human endothelial cell line ECV304.  II.  Functional responses of the ECV304 cells]. 
Functional responses of the spontaneously transformed human endothelial cell line ECV304 were studied in order to asses its applicability as an endothelial cell model for studying angiogenesis and signal transduction.  The dependence of proliferation activity of this line on the presence of growth factor was shown.  The absent serum in culture medium resulted in blocking of cells in G1-phase of a cell cycle which is not typical for tumor cell lines.  Low doses of beta particles emitted during [3H]thymidine decay resulted in blocking the proliferation of these cells in G2M-phase in a dose-dependent manner.  Incubation of the cells with another source of beta particles, 3H2O, under condition of equal specific activities of tritium resulted in preferable accumulation of the cells in S-phase.  The different efficiency of beta particles of tritium as a part of 3H2O molecule or thymidine demonstrates that various mechanisms are responsible for various check points.  The check point of G1/S is absent and that complies with the presence of deletion of chromosome 9 in locus p21.  The level of NO produced by constitutive form of NO-synthase in ECV304 cells was relatively low and not modified by inducible NO-synthase inhibitors.  The data obtained suggest that ECV304 line cells retained the properties of the initial spontaneously transformed cell line obtained from human umbilical vein (HUVEC) as well as they can be used as a model system for further studies of the properties of vascular endothelial.