Comparison of insulin and insulin-like growth factor I receptors from rat skeletal muscle and L-6 myocytes |
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Authors: | C F Burant M K Treutelaar K D Allen D A Sens M G Buse |
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Affiliation: | 1. Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Super Highway, Gadap Road, Karachi 74600, Pakistan;2. Central Drug Laboratories, Ministry of Health, DRAP, Block-B, S.M.C.H., Karachi 74400, Pakistan |
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Abstract: | Insulin and IGF-I receptors were solubilized from fused L-6 myocytes, a rat skeletal muscle derived cell line, and compared to rat skeletal muscle receptors. In skeletal muscle, 125I-insulin binding was competed by insulin greater than IGF-I greater than MSA, whereas in L-6 cells IGF-I greater than insulin greater than MSA. 125I-IGF-I binding was competed by IGF-I greater than insulin = MSA in both tissues. On electrophoresis, differences in Mr were observed between skeletal muscle and L-6 derived receptors both in the alpha- and beta-subunits. Six antibodies directed against the human insulin receptor beta-subunit recognized the rat skeletal muscle insulin receptor, while only two reacted strongly with L-6 derived receptors. Skeletal muscle has receptors with relative specificity for insulin and IGF-I respectively; L-6 cells also have two classes of receptors, one is kinetically similar to the IGF-I receptor from skeletal muscle; the other, which binds insulin with relatively high affinity has even greater affinity for IGF-I. This unusual receptor may represent a developmental stage in muscle or the transformed nature of L-6 cells. |
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