The Role of C-Terminus of Insulin B Chain and the Amino Group of B29Lys Side Chain in the Growth Promoting Activities of Insulin.

By growing the mouse mammary tumor-derived cell line GR2H6 in 96-well plates, we have developed an in vitro bioassay for the growth promoting activities of insulin. This bioassay system offers several advantages over currently used alternatives, such as higher sensitivity, better reproducibility and the processing of many samples simultaneously. Using this method, the mitogenic activities of insulin and its analogues were studied. The analogue with elongated C-tenminus of insulin B chain ( B31Lys Ins-NH(2)) had a higher mitogenic activity than insulin (130% of insulin). The mitogenic activities of analogues with B29Lys amino group blocked was one third of those with B29Lys amino group free, indicating that the C-terminal part of B chain and the amino group of B29Lys were important for the growth promoting activities of insulin.