Hasil untuk "physics.comp-ph"

W. Waddell, T. Butler

Ryo Kanzaki, Tomoya Hidaka, Shinji Tajima et al.

Donald E. Williams, R. Reisfeld

T. Demeester, Ching-I Wang, J. Wernly et al.

A. Bérod, B. K. Hartman, J. Pujol

W. Boron, E. Boulpaep

We have used pH-, Na-, and Cl-sensitive microelectrodes to study basolateral HCO3- transport in isolated, perfused proximal tubules of the tiger salamander Ambystoma tigrinum. In one series of experiments, we lowered basolateral pH (pHb) from 7.5 to 6.8 by reducing [HCO3-]b from 10 to 2 mM at a constant pCO2. This reduction of pHb and [HCO3-]b causes a large (approximately 0.35), rapid fall in pHi as well as a transient depolarization of the basolateral membrane. Returning pHb and [HCO3-]b to normal has the opposite effects. Similar reductions of luminal pH (pHl) and [HCO3-]l have only minor effects. The reduction of [HCO3-]b and pHb also produces a reversible fall in aiNa. In a second series of experiments, we reduced [Na+]b at constant [HCO3-]b and pHb, and also observed a rapid fall in pHi and a transient basolateral depolarization. These changes are reversed by returning [Na+]b to normal. The effects of altering [Na+]l in the presence of HCO3-, or of altering [Na+]b in the nominal absence of HCO3-, are substantially less. Although the effects on pHi and basolateral membrane potential of altering either [HCO3-]b or [Na+]b are largely blocked by 4-acetamido-4-isothiocyanostilbene-2,2'-disulfonate (SITS), they are not affected by removal of Cl-, nor are there accompanying changes in aiCl consistent with a tight linkage between Cl- fluxes and those of Na+ and HCO3-. The aforementioned changes are apparently mediated by a single transport system, not involving Cl-. We conclude that HCO3- transport is restricted to the basolateral membrane, and that HCO3- fluxes are linked to those of Na+. The data are compatible with an electrogenic Na/HCO3 transporter that carries Na+, HCO3-, and net negative charge in the same direction.

J. D. Johnson, D. Epel, M. Paul

M. Chesler

Abbreviations

D. Spray, Andrew L. Harris, Michael V. L. Bennett

J. Russell, D. Dombrowski

N. Revsbech, B. B. Jørgensen, T. Henry Blackburn et al.

F. A. Smith, J. Raven

W. Moolenaar

Lilian Nagle, Skye Brown, Arianna Krinos et al.

K. Soppimath, D. Tan, Y.‐Y. Yang

K. Toews, R. Shroll, C. Wai et al.

Li-ning Sun, Hongshang Peng, Matthias I. J. Stich et al.

R. Bashir, J. Z. Hilt, Oguz H. Elibol et al.

S. Uchiyama, N. Kawai, A. de Silva et al.

O. Kreft, A. M. Javier, G. Sukhorukov et al.