AJP - Renal Physiology, Vol 245, Issue 3 374-F381, Copyright © 1983 by American Physiological Society
Sodium-dependent succinate transport in renal outer cortical brush border membrane vesicles
Y. Fukuhara and R. J. Turner
The transport of succinate into outer cortical brush border membrane
vesicles (early proximal tubule) was studied. Succinate is taken up into an
osmotically active space and exhibits the same distribution volume and the
same degree of nonspecific binding and trapping as D-glucose. Succinate
uptake is markedly enhanced by sodium and slightly enhanced by lithium but
shows no stimulation by other monovalent cations tested. Kinetic analysis
of the sodium-dependent component of succinate flux indicates a single
transport site obeying Michaelis-Menten kinetics (Km = 1 mM and Vmax = 50
nmol X min -1 X mg protein -1 as measured under zero trans conditions at
100 mM NaCl and 28 degrees C with delta psi = 0). Direct evidence is given
that succinate transport is coupled to sodium and is rheogenic, involving
the net transfer of positive charge. The sodium:succinate coupling
stoichiometry is found to be 2:1 by two independent methods.
