Key result
Ovine somatomedin binds like IGF-I, revealing type I and II IGF receptors on muscle satellite cells.
Why the study?
The binding characteristics of ovine somatomedin and multiplication stimulating activity/rat insulin-like growth factor II with skeletal muscle satellite cell receptors were not fully described.
This preclinical study demonstrates that primary cultures of skeletal muscle satellite cells possess both type I and type II IGF receptors, with ovine somatomedin exhibiting binding characteristics similar to IGF-I.
Insulin enhances MSA binding to satellite cells only at high doses; leaves open any role in muscle physiology or therapy.
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 micrograms/l had no effect on the subsequent binding of 125I-oSm. Preincubation 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.
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Dodson et al. (1987) studied this question. 125I-multiplication stimulating activity (MSA) and 125I-ovine somatomedin was evaluated on Receptor binding characteristics. Ovine somatomedin exhibits binding characteristics similar to IGF-I, indicating that primary cultures of skeletal muscle satellite cells possess type I and type II IGF receptors.