Interaction of ovine somatomedin and multiplication stimulating activity/rat insulin-like growth factor II with cultured skeletal muscle satellite cells

The interactions of ¹²⁵I-multiplication stimulating activity (MSA) and ¹²⁵I-ovine somatomedin with receptors on skeletal muscle satellite cells are described. Specific binding of ¹²⁵I-MSA/rIGF-II was inhibited by MSA/rIGF-II and oSm but not by insulin. Binding of ¹²⁵I-oSm was inhibited by MSA/rIGF-II, oSm and insulin. In addition, 24-h pre-incubation of satellite cells with insulin increased the amount of ¹²⁵I-MSA/rIGF-II bound, but insulin concentrations below 550 μg/l had no effect on the subsequent binding of ¹²⁵I-oSm. Pre-incubation of cultures with oSm or MSA/rIGF-II decreased the subsequent binding of ¹²⁵I-oSm and ¹²⁵I-MSA/rIGF-II. These preliminary experiments suggest that oSm is similar to IGF-I in its binding characteristics and that primary cultures of skeletal muscle satellite cells possess type I and type II IGF receptors.