Studies on the mitogenic effect of transferrin by membrane signal transduction

One of the earliest events leading to cell activation and growth is the hydrolysis of inositol phospholipids producing various membrane signals induced by an interaction between growth factors or hormones with their respective receptors on the cell membrane 1]. To demonstrate the mitogenio action of transferrin, our results show that an addition of transferrin to "serum-deprived" rat hepatoma cells produced a rapid but transient rise in inositol 1, 4, 5-trisphosphate (IP3) level, and at the same time, an increased intraoellular Oa2 activity and a oytoplasmic alkalinization were observed. These signal transduo-tions further lend support to the mitogenic nature of transferrin. In addition, a possible link between the receptor-mediated endocytosis of transferrin with the generation of intraoellular signals is discussed herewith.