title: Effect of insulin on intracellular pH in frog skeletal muscle fibers.
abstract: The effect of insulin on intracellular pH (pHi) and membrane potential was studied in frog semitendinosus muscle fibers, using recessed-tip pH-sensitive glass microelectrodes and conventional 3 M KCl-filled microelectrodes. After a lag period of approximately 20 min, insulin [1 mU/ml, 0.1% bovine serum albumin (BSA)] produced a slow hyperpolarization of 2-5 mV and an alkalinization of 0.05-0.10 pH unit, which were both completed within 1 h and were not reversed by washing in insulin-free solution for 1 h. The effect of insulin on the pHi recovery rate from CO2-induced acidification was examined at various membrane voltages. At normal membrane voltage, insulin (400 mU/ml, no BSA) slightly increased the slow pHi recovery (from 0.01 to 0.04 delta pH/h). In fibers depolarized in 15 mM K to about -50 mV, insulin nearly tripled the recovery rate (from 0.05 to 0.13 delta pH/h). This insulin-induced recovery was abolished by 1 mM amiloride, a Na-H exchange inhibitor. The increased pHi recovery in 15 mM K thus represents an increased Na-H exchange, which may be due to an interaction between insulin and either membrane depolarization, per se, or increased intracellular Ca. In fibers depolarized in 50 mM K to about -25 mV, insulin did not affect recovery (0.28 delta pH/h). This lack of insulin effect might be due to fiber swelling or to the difference in the time course of elevation of intracellular Ca at -25 and -50 mV. These results are consistent with an alkalinizing effect of insulin in frog muscle mediated by Na-H exchange.
authors.forename: R W
authors.initials: RW
authors.lastname: Putnam
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000494:pharmacology*; D007473:Ion Channels / Q000187:drug effects* / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D008839:Microelectrodes; D009132:Muscles / Q000187:drug effects / Q000378:metabolism*; D011894:Rana pipiens; D012964:Sodium / Q000378:metabolism*; D013997:Time Factors
chemical_list: D007328:Insulin; D007473:Ion Channels; D000584:Amiloride; D012964:Sodium; D002118:Calcium