Influence of different corpus luteum fractions on the DNA synthesis of cultivated fibroblasts, medial, and endothelial cells.

Porcine and bovine corpora lutea contain an activity capable of stimulating the initiation of DNA synthesis of mouse embryo fibroblasts, calf aorta media cells, and calf aorta endothelial cells. After fractionation of extracts produced by gradual ammonium sulfate precipitation by means of ion exchange chromatography on CM-Sephadex the activity is especially enriched in the last fraction (peak 5). The initiation of the DNA synthesis of calf aorta endothelial cells, however, is strongly dependent on the concentration of the labelled thymidine in the incubation medium. Calf aorta endothelial cells significantly respond to this corpus luteum factor only at a reduced 3H-thymidine concentration of 9.25 nM. At a 3H-thymidine concentration of 37 nM at which mouse embryo fibroblasts and calf aorta media cells respond with a dose-dependent stimulation of DNA synthesis, calf aorta endothelial cells only show a dose-dependent inhibition of the 3H-thymidine incorporation into the DNA. The relationship of this factor to the known growth factors and to the corpus luteum angiogenic factor (CLAF) deserves further investigation.