Oxalate:OH exchange across rat renal cortical brush border membrane.
We demonstrated the presence of oxalate:OH exchange in rat renal brush border membrane. Transient concentrative uptake of oxalate ("overshoot") was observed in the presence of an inside alkaline (pH = 8.5 inside, 6.5 outside) pH gradient, but this pH gradient-stimulated oxalate uptake was abolished by 1 mM DIDS, indicating that DIDS-sensitive and -insensitive oxalate uptake mechanisms were present. The DIDS-sensitive oxalate uptake was temperature-dependent and saturable with a Km of 0.0365 mM and a Vmax of 1.38 nmol.30 second-1.mg protein-1. In addition, oxalate was transported into the osmotically active internal space. In the presence of the pH gradient, a change in transmembrane potential had no effect on pH gradient-stimulated oxalate uptake. Oxalate was exchanged for OH and this exchange was sensitive to inhibition by DIDS. Inhibition by DIDS, furosemide and probenecid facilitated the distinction of oxalate:OH exchange from formate:Cl and oxalate:Cl exchange. In preparation of our brush border membrane vesicles, no apparent SO4:HCO3 exchange was present. These data indicate that oxalate:OH exchange occurs on the brush border membrane.
Yamakawa
K
K
Department of Urology, Mie University School of Medicine, Tsu, Japan.
Kawamura
J
J
D000818:Animals; D001693:Biological Transport, Active; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000378:metabolism; D066298:In Vitro Techniques; D007474:Ion Exchange; D007672:Kidney Cortex / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008871:Microvilli / Q000378:metabolism; D010070:Oxalates / Q000378:metabolism*; D019815:Oxalic Acid; D051381:Rats; D011919:Rats, Inbred Strains
D006878:Hydroxides; D010070:Oxalates; C031356:hydroxide ion; D019815:Oxalic Acid