Mechanism of mercurial inhibition of sodium-coupled alanine uptake in liver plasma membrane vesicles from Raja erinacea

Journal Article · Fri Feb 01 04:00:00 EST 1991 · Toxicology and Applied Pharmacology; (USA)

DOI:https://doi.org/10.1016/0041-008X(91)90216-2· OSTI ID:6139209

Sellinger, M; Ballatori, N; Boyer, J L ^[1]

---

1. Mount Desert Island Biological Laboratory, Salsbury Cove, ME (USA)

In mammalian hepatocytes the L-alanine carrier contains a sulfhydryl group that is essential for its activity and is inhibited by mercurials. In hepatocytes of the evolutionarily primitive little skate (Raja erinacea), HgCl2 inhibits Na(+)-dependent alanine uptake and Na+/K(+)-ATPase and increase K+ permeability. To distinguish between direct effects of HgCl2 on the Na(+)-alanine cotransporter and indirect effects on membrane permeability, (3H)alanine transport was studied in plasma membrane vesicles. (3H)Alanine uptake was stimulated by an out-to-in Na+ but not K+ gradient and was saturable confirming the presence of Na(+)-alanine cotransport in liver plasma membranes from this species. Preincubation of the vesicles with HgCl2 for 5 min reduced initial rates of Na(+)-dependent but not Na(+)-independent alanine uptake in a dose-dependent manner (10-200 microM). In the presence of equal concentrations of NaCl or KCl inside and outside of the vesicles, 75 microM HgCl2 directly inhibited sodium-dependent alanine-(3H)alanine exchange, demonstrating that HgCl2 directly affected the alanine cotransporter. Inhibition of Na(+)-dependent alanine uptake by 30 microM HgCl2 was reversed by dithiothreitol (1 mM). HgCl2 (10-30 microM) also increased initial rates of 22Na uptake (at 5 sec), whereas 22Na uptake rates were decreased at HgCl2 concentrations greater than 50 microM. Higher concentrations of HgCl2 (100-200 microM) produced nonspecific effects on vesicle integrity. These studies indicate that HgCl2 inhibits Na(+)-dependent alanine uptake in skate hepatocytes by three different concentration-dependent mechanisms: direct interaction with the transporters, dissipation of the driving force (Na+ gradient), and loss of membrane integrity.

• OSTI ID: 6139209
• Journal Information: Toxicology and Applied Pharmacology; (USA), Journal Name: Toxicology and Applied Pharmacology; (USA) Vol. 107:2; ISSN TXAPA; ISSN 0041-008X
• Country of Publication: United States
• Language: English

Related Subjects

550501 -- Metabolism-- Tracer Techniques
560300* -- Chemicals Metabolism & Toxicology
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ACID ANHYDRASES
ALANINES
ALKALI METAL COMPOUNDS
ALKALI METAL ISOTOPES
AMINO ACIDS
ANIMALS
AQUATIC ORGANISMS
ATP-ASE
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
BIOLOGICAL EFFECTS
BODY
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CELL MEMBRANES
DIGESTIVE SYSTEM
DOSE-RESPONSE RELATIONSHIPS
ELEMENTS
ENZYMES
FISHES
GLANDS
HYDROGEN COMPOUNDS
HYDROLASES
INHIBITION
ISOMERIC TRANSITION ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
LIVER
MEMBRANE TRANSPORT
MEMBRANES
MERCURY
METALS
NUCLEI
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
PERMEABILITY
PHOSPHOHYDROLASES
POTASSIUM COMPOUNDS
RADIOISOTOPES
SODIUM 22
SODIUM COMPOUNDS
SODIUM ISOTOPES
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES
YEARS LIVING RADIOISOTOPES