Interactions of (/sup 14/C)phosphonoformic acid with renal cortical brush-border membranes. Relationship to the Na+-phosphate co-transporter

Journal Article · Mon Jun 15 00:00:00 EDT 1987 · J. Biol. Chem.; (United States)

OSTI ID:6075518

Szczepanska-Konkel, M; Yusufi, A N; Dousa, T P

Since phosphonoformic acid (PFA) acts as a specific competitive inhibitor of Na+-Pi co-transport across renal brush-border membrane (BBM), we employed the (/sup 14/C)PFA as a probe to determine the mechanism of its interaction with rat renal BBM. The binding of (/sup 14/C)PFA to BBM vesicles (BBMV), with Na+ present in extravesicular medium (Na+o), was time- and temperature-dependent. The replacement of Na+o with other monovalent cations reduced the PFA binding by -80%. Cl- was the most effective accompanying monovalent anion as NaCl for maximum PFA binding. The Na+o increased the apparent affinity of BBMV for (/sup 14/C)PFA binding, but it did not change the maximum binding capacity. The maximum (/sup 14/C)PFA binding was achieved at Na+o approximately equal to 50 mM. The extent of Na+-dependent (/sup 14/C)PFA binding correlated with percent inhibition by an equimolar dose of PFA of the dependent BBMV uptake of 32Pi. Intravesicular Na+ (Na+i) decreased (/sup 14/C)PFA binding, on BBMV, and this inhibition by Na+i was dependent on the presence of Na+o. The increase in Na+i, at constant (Na+)o, decreased the Vmax, but not the Km, for (/sup 14/C)PFA binding on BBMV. Bound (/sup 14/C)PFA was displaced from BBMV by phosphonocarboxylic acids proportionally to their ability to inhibit gradient-dependent Pi transport, whereas other monophosphonates, diphosphonates, L-proline, or D-glucose did not influence the (/sup 14/C)PFA binding. The Na+-dependent binding of (/sup 14/C)PFA and of (/sup 3/H)phlorizin by BBMV was 10 times higher than binding of these ligands to renal basolateral membranes and to mitochondria. (/sup 14/C)PFA probably binds onto the same locus on the luminal surface of BBM, where Pi and Na+ form a ternary complex with the Na+-Pi co-transporter.

• Research Organization: Mayo Clinic, Rochester, MN
• OSTI ID: 6075518
• Journal Information: J. Biol. Chem.; (United States), Vol. 262:17
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
FORMIC ACID
BIOCHEMICAL REACTION KINETICS
PHOSPHATES
MEMBRANE TRANSPORT
SODIUM COMPOUNDS
AFFINITY
ANIONS
CARBON 14 COMPOUNDS
CATIONS
CELL MEMBRANES
KIDNEYS
LIGANDS
PHOSPHORUS 32
RATS
TEMPERATURE DEPENDENCE
TIME DEPENDENCE
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ALKALI METAL COMPOUNDS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHARGED PARTICLES
DAYS LIVING RADIOISOTOPES
IONS
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LABELLED COMPOUNDS
LIGHT NUCLEI
MAMMALS
MEMBRANES
MONOCARBOXYLIC ACIDS
NUCLEI
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
OXYGEN COMPOUNDS
PHOSPHORUS COMPOUNDS
PHOSPHORUS ISOTOPES
RADIOISOTOPES
REACTION KINETICS
RODENTS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques