Studies on purification of oestrogen-induced protein from rat uterus and its physiological role in cultured cells.

This paper presents evidence to show the presence of an oestrogen-induced protein (IP) from rat uterus which is able to stimulate the incorporation of 3H-thymidine into DNA of 3T6 fibroblasts in vitro. The purified uterine protein fraction has been shown th contain less than 10 detectable proteins. The molecular weight of IP band is about 50,000 Daltons with an iso-electric point of 4.5. Comparison of oestrogen-treated and -untreated uterine cytosols on SDS-acrylamide gel electrophoresis indicates that the IP band is also present in the untreated controls. It is therefore suggested that the oestrogen-induced protein may be analogous or identical to the growth-promoting protein synthesized by LX cells.