RESUMO
The growth of MCF-7 cells, established from a metastatic mammary carcinoma, and of HBL-100 cells, derived from a primary culture of human milk, was examined in medium supplemented with whole blood serum (WBS), defibrinogenated plasma, and plasma-derived serum (PDS). PDS obtained from platelet-poor plasma collected with the anticoagulant citrate phosphate dextrose and clotted by the addition of calcium chloride did not promote the growth of MCF-7 cells as well as did WBS or platelet-poor defibrinogenated plasma alone. Growth-inhibitory activity was observed when final cell densities in the presence of PDS combined with fetal bovine serum (FBS) were compared with those in control cultures maintained in FBS alone. The level of this activity in PDS varied among donors. Inhibition was not observed with HBL-100 cells. Calcium chloride did not induce inhibitory activity when added to WBS or defibrinogenated plasma, and platelet components did not alter the level of inhibition in PDS. However, platelet extracts did affect the expression of inhibition when added to plasma before clotting. Activity was diminished following dialysis of PDS, which suggested that inhibition stemmed from a small-molecular-weight factor for which expression depended on the mechanism of plasma coagulation.