Receptors for insulin and insulin-like growth factor in cultured arterial smooth muscle cells depend on their growth state

Abstract

The binding of 125I-labelled insulin and 125I-labelled insulin-like growth factor (IGF) to cultured arterial smooth muscle cells from rats was studied during various growth states of the cells. The level of binding of 125I-labelled insulin to the cells was low in growing cells and high in stationary cells. The level of 125I-labelled IGF binding to the cells was high in growing cells and low in stationary cells. In addition, the effect of unlabelled IGF and insulin on the binding of both 125I-labelled hormones to the cells was examined during various growth states. In growing cells insulin displaced 125I-labelled insulin from its binding sites; IGF competed weakly with 125I-labelled insulin for the binding sites. In parallel, IGF displaced 125I-labelled IGF binding whereas insulin competed weakly with 125I-labelled IGF for the binding sites. In stationary cells both hormones displaced 125I-labelled IGF binding. Insulin-like growth factor also displaced 125I-labelled insulin binding whereas insulin could not significantly displace 125I-labelled insulin from the binding sites. Insulin only competed with 125I-labelled insulin for the binding sites after removal of the fetal calf serum from the culture medium.