PEPTIDIC COMPONENTS OF SHEEP AMNIOTIC-FLU ID REGULATE CELL-PROLIFERATION OF BP-A31 CELLS

Cell proliferation and differentiation of developing fetus is influenc ed by hormones as well as insulin-like growth factors and their bindin g proteins contained in amniotic fluid. Our purpose was to study the a ctual mitogenic activity of proteins and peptides present in the sheep amniotic fluid. The cell cycle regulatory activity was estimated by u sing mouse fibroblasts BP-A31 as target cells. The whole amniotic flui d was inactive. However, after removal of small molecules on Sephadex G-10, the fraction eluted in the void volume (M-r greater than or equa l to 0.7 kDa) was able to induce the cell division cycle in a signific ant proportion of quiescent fibroblasts (Fig. 1, fraction A; Fig. 2). By further gel chromatography of this active fraction at acidic condit ion on Sephadex G-50, two components with mitogenic activity were sepa rated. One component was eluted immediately after the void volume of t he column, the other one was coeluted with I-125-IGF-I (Fig. 3). The f unctional characteristics of mitogenic signal of both components (sens itivity to mitogenic effecters) were similar to those of IGF-I and ins ulin (Fig. 4). We suppose that a component with higher molecular weigh t eluted in the vicinity of the void volume of Sephadex G-50 represent s probably IGFBPs or other similar proteins.