Abstract
The absorption of the lipophilic anions dipycrilamine (DPA-) and tetraphenylborate (TPhB-) by the lipid matrix of the squid axon membrane, and the kinetics of their translocation, were studied by the charge pulse relaxation technique. The axons were treated with tetrodotoxin (TTX) and 4-aminopyridine to block the ionic currents responsible for nerve excitation. At high enough concentrations of absorbed ions (∼ 10-12 mol/cm2) the membrane voltage relaxation following a brief current pulse consisted mainly of two exponential components, whose time constants and relative amplitudes were used for estimating the translocation rate constant, K, and the density of absorbed ions, N. These measurements were performed at different hydrostatic pressures in the range 1–100 MPa (∼ 1,000 atm), and at different temperatures in the range 5° C–20° C. Both K and N were found to be little affected by pressure. The pressure dependence of K indicated that the translocation of lipophilic ions across the nerve membrane involves activation volumes of the order of 5 cm3/mol. In all experiments the passive membrane resistance was little affected by pressures up to 80 MPa. However, above 100 MPa it fell dramatically to low values, presumably because of phase separation phenomena between the membrane components. The temperature dependence of K, both for DPa- and TPhB-, implied an activation energy for ion translocation of the order of 60 kJ/mol, close to that measured in artificial lipid bilayers.
It is concluded that the lipid bilayer structure of the nerve membrane is not modified by pressures below 80 MPa and that the intramembrane movements of relatively small charged groups cannot account for the large activation volumes involved in the gating of ionic channels.
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References
Almers W (1978) Gating currents and charge movements in excitable membranes. Rev Physiol Biochem Pharmacol 82: 96–182
Andersen OS, Feldberg S, Nakadomari H, Levy S, McLaughlin S (1978) Electrostatic interactions among hydrophobic ions in lilid bilayer membranes. Biophys J 21: 35–70
Andersen OS, Fuchs M (1975) Potential energy barriers to ion transport within lipid bilayers. Studies with tetraphenylborate. Biophys J 15: 795–830
Benz R, Conti F (1981) Structure of the squid axon membrane as derived from charge-pulse relaxation studies in the presence of absorbed lipophilic ions. J Membr Biol 59: 91–104
Benz R, Cros D (1978) Influence of sterols on ion transport through lipid bilayer membranes. Biochim Biophys Acta 506: 265–280
Benz R, Gisin BF (1978) Influence of membrane structure on ion transport through lipid membranes. J Membr Biol 40: 293–314
Benz R, Läuger P (1976) Kinetic analysis of carrier-mediated ion transport by the charge-pulse technique. J Membr Biol 27: 171–191
Benz R, Läuger P (1977) Transport kinetics of dipicrylamine through lipid bilayer membranes. Effects of membrane structure. Biochim Biophys Acta 468: 245–258
Benz R, Nonner W (1981) Structure of the axolemma of frog myelinated nerve: Relaxation experiments with a lipophilic probe ion. J Membr Biol 59: 127–134
Benz R, Zimmermann U (1983) Evidence for the presence of mobile charges in the cell membrane of Valonia ultricularis. Biophys J 43: 13–26
Benz R, Conti F, Fioravanti R (1983) Pressure dependence of lipophilic ion translocation across the squid axon membrane. Atti VI Congresso SIBPA-VII Congresso GNCB, Camogli, pp 33–34
Benz R, Läuger P, Janko K (1976) Transport kinetics of hydrophobic ions in lipid bilayer membranes. Charge pulse relaxation studies. Biochim Biophys Acta 455: 701–720
Bruner LJ (1975) The interaction of hydrophobic ions with lipid bilayer membranes. J Membr Biol 22: 125–141
Chandler WK, Meves H (1965) Voltage clamp experiments on internally perfused giant axons. J Physiol (London) 180: 788–820
Conrad MJ, Singer SJ (1979) Evidence for a large internal pressure in biological membranes. Proc Natl Acad Sci USA 76: 5202–5206
Conti F, Fioravanti R, Segal JR, Stühmer W (1982a) Pressure dependence of the sodium currents of squid giant axon. J Membr Biol 69: 23–34
Conti F, Fioravanti R, Segal JR, Stühmer W (1982b) Pressure dependence of the potassium currents of squid giant axon. J Membr Biol 69: 35–40
Ebbecke V, Schaefer H (1935) Über den Einfluß hoher Drücke auf den Aktionsstrom von Muskeln und Nerven. Pfluegers Arch Ges Physiol 236: 678–692
Fernandez JM, Taylor RE, Bezanilla F (1983) Induced capacitance in the squid giant axon. J Gen Physiol 82: 331–346
Grundfest H (1936) Effects of hydrostatic pressure upon the excitability, the recovery and the potential sequence of frog nerve. Cold Spring Harbor Symp. Quant. Biol 5: 179–187
Henderson JV, Gilbert DL (1975) Slowing of ionic currents in the voltage clamped squid axon by helium pressure. Nature (London) 258: 351–352
Johnson FJ, Eyring H, Stover B (1974) The theory of rate processes in biology and medicine. John Wiley, New York
Jordan PC, Stark G (1979) Kinetics of transport of hydrophobic ions through lipid membranes including diffusion polarization in the aqueous phase. Biophys Chem 10: 273–287
Neumcke B, Läuger P (1969) Nonlinear electrical effects in lipid bilayer membranes. Biophys J 9: 1160–1170
Parsegian A (1969) Energy of an ion crossing a low dielectric membrane. Solutions of four relevant electrostatic problems. Nature (London) 221: 844
Spyropoulos CS (1957a) Responses of single nerve fibers at different hydrostatic pressures. Am J Physiol 189: 214–218
Spyropoulos CS (1957b) The effects of hydrostatic pressure upon the normal and narcotizated nerve fiber. J Gen Physiol 40: 849–857
Wann KT, Macdonald AG (1980) The effects of pressure on excitable cells. Comp Biochem Physiol 66A: 1–12
Yeh JZ, Oxford GS, Wu CH, Narahashi T (1976) Dynamics of aminopyridine block of potassium channels in squid axon membrane. J Gen Physiol 68: 519–535
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Benz, R., Conti, F. & Fioravanti, R. Extrinsic charge movement in the squid axon membrane. Eur Biophys J 11, 51–59 (1984). https://doi.org/10.1007/BF00253858
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DOI: https://doi.org/10.1007/BF00253858