Dependence of cell pH and buffer capacity on the extracellular acid-base change in the skeletal muscle of bullfrog.
Intracellular pH was measured with single- or double-barreled liquid ion-exchanger microelectrodes in the bullfrog sartorius muscle perfused in vitro. A neutral carrier ligand was used for pH sensor of microelectrodes. Average slopes of the single-barreled microelectrodes were -56.4 +/- 1.34 mV/pH (n = 30) and the double-barreled -52.6 +/- 1.34 mV/pH (n = 65). While changing acid-base parameters of bathing media (pHe from 6.7 to 8.4, PCO2 from 3.7 to 37 mmHg, and HCO3- concentrations from 5 to 75 mM), paired muscle cell pH (pHi) and membrane potential (EM) values were determined at 23 degrees C. In control conditions (pHe = 7.6, HCO3- = 15 mM, PCO2 = 11 mmHg), pHi and EM (n = 20) averaged 6.99 +/- 0.04 (S.E.) and -69.2 +/- 2.2 mV, respectively. A negative correlation was observed between pHi and EM (correlation coefficient r = -0.564, p less than 0.002). The change in EM per unit pH change was approximately -30mV, indicating that the H+ distribution across the cell membrane only incompletely obeys the Donnan rule. The pHi varied more or less with pHe. Namely, changes in pHe and PCO2 at constant HCO3- produced relatively large changes in pHi, but elevation of pHe and HCO3- at constant PCO2 produced relatively minor rise in pHi. The stability of pHi or the size of buffer capacity were proportional to external HCO3- concentrations. These data suggested that a transmembrane distribution of buffer pairs depends largely on non-ionic diffusion of CO2-HCO3- buffer system and partly on ion fluxes of HCO3- or H+.
Fujimoto
M
M
Department of Physiology, Osaka Medical College, Japan.
Morimoto
Y
Y
Kubota
T
T
D000136:Acid-Base Equilibrium / Q000187:drug effects*; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology; D002021:Buffers; D002245:Carbon Dioxide / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D008839:Microelectrodes; D009132:Muscles / Q000187:drug effects*; D009994:Osmolar Concentration; D011892:Rana catesbeiana
D001639:Bicarbonates; D002021:Buffers; D002712:Chlorides; D002245:Carbon Dioxide