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Insulin stimulation of Na/H antiport in L‐6 cells: A different mechanism in myoblasts and myotubes
Author(s) -
Incerpi Sandra,
Rizvi Syed I.,
De Vito Paolo,
Luly Paolo
Publication year - 1997
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/(sici)1097-4652(199706)171:3<235::aid-jcp1>3.0.co;2-p
Subject(s) - myogenesis , antiporter , myocyte , protein kinase c , insulin , endocrinology , medicine , intracellular , tyrosine kinase , biology , chemistry , microbiology and biotechnology , biochemistry , kinase , signal transduction , membrane
Insulin modulation of the Na/H antiport of L‐6 cells, from rat skeletal muscle was studied in both myoblasts and myotubes using the fluorescent, pH sensitive, intracellular probe 2′,7′ bis (carboxyethyl)‐5(6)‐carboxyfluorescein. Insulin stimulated the Na/H antiport activity in L‐6 cells, showing a bell‐shaped dose response typical of other insulin responses: a maximum at 10 nM (ΔpH of 0.132 ± 0.007 and 0.160 ± 0.040 over basal value, for myoblasts and myotubes, respectively; means ± SD, n = 6–8) and smaller effects at higher and lower concentrations. Phorbol 12‐myristate 13‐acetate (PMA), an activator of protein kinase C, also stimulated the antiport in myoblasts but not in myotubes. Surprisingly the rapid increase in intracellular pH was not observed when insulin and PMA were added simultaneously to myoblasts; apparently these two activators mutually excluded each other. Downregulation of protein kinase C, obtained by preincubation of cells with PMA for 20 hr, totally abolished both hormone and PMA effects in myoblasts, whereas in myotubes insulin stimulation was not affected. Inhibitors of tyrosine kinase activity, such as erbstatin analog and genistein abolished insulin effect on the Na/H antiport, both in myoblasts and in myotubes. Different sensitivity to pertussis toxin in the two cell types suggests that the differentiation process leads to a change in the signal pathways involved in the physiological response to insulin. J. Cell. Physiol. 171:235–242, 1997. © 1997 Wiley‐Liss, Inc.