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Insulin‐like growth factor‐1 enhances rat skeletal muscle charge movement and L‐type Ca 2+ channel gene expression
Author(s) -
Wang ZhongMin,
Laura Messi María,
Renganathan Muthukrishnan,
Delbono Osvaldo
Publication year - 1999
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1999.0331v.x
Subject(s) - skeletal muscle , medicine , endocrinology , activator (genetics) , voltage dependent calcium channel , dissociation constant , chemistry , gene expression , insulin like growth factor , growth factor , myocyte , biology , microbiology and biotechnology , calcium , gene , receptor , biochemistry
1 We investigated whether insulin‐like growth factor‐1 (IGF‐1), an endogenous potent activator of skeletal muscle proliferation and differentiation, enhances L‐type Ca 2+ channel gene expression resulting in increased functional voltage sensors in single skeletal muscle cells. 2 Charge movement and inward Ca 2+ current were recorded in primary cultured rat myoballs using the whole‐cell configuration of the patch‐clamp technique. Ca 2+ current and maximum charge movement ( Q max ) were potentiated in cells treated with IGF‐1 without significant changes in their voltage dependence. Peak Ca 2+ current in control and IGF‐1‐treated cells was ‐7·8 ± 0·44 and ‐10·5 ± 0·37 pA pF −1 , respectively ( P < 0·01), whilst Q max was 12·9 ± 0·4 and 22·0 ± 0·3 nC μF −1 , respectively ( P < 0·01). 3 The number of L‐type Ca 2+ channels was found to increase in the same preparation. The maximum binding capacity ( B max ) of the high‐affinity radioligand [ 3 H]PN200‐110 in control and IGF‐1‐treated cells was 1·21 ± 0·25 and 3·15 ± 0·5 pmol (mg protein) −1 , respectively ( P < 0·01). No significant change in the dissociation constant for [ 3 H]PN200‐110 was found. 4 Antisense RNA amplification showed a significant increase in the level of mRNA encoding the L‐type Ca 2+ channel α1‐subunit in IGF‐1‐treated cells. 5 This study demonstrates that IGF‐1 regulates charge movement and the level of L‐type Ca 2+ channel α1‐subunits through activation of gene expression in skeletal muscle cells.