Copper transport and kinetics in cultured c6 rat glioma cells.
Qian, Yongchang, Evelyn Tiffany-Castiglioni, Edward D. Harris.
Department of Biochemistry and Biophysics, Texas A&M University,
College Station, TX 77843; Department of Veterinary Anatomy and
Public Health, Texas A&M University, College Station, TX 77843
APStracts 2:0197C, 1995.
C6 rat glioma cells accumulate and efflux 67Cu. Both processes showed
saturation kinetics with increasing [67Cu]. The Km for uptake was
0.63+/-0.14 [mu]M; Vmax was 3.29+/-0.57 pmol Cu/mg protein/min. The
Km for efflux was 0.15+/-0.06 [mu]M; Vmax was 1.08+/-0.71 pmol Cu/mg
protein/min. p-chloromercuribenzoate (PCMB) totally blocked 67Cu
efflux but had no effect on Km or Vmax of uptake. Total 67Cu in the
cell after 50 min was partitioned equally between particulate and
soluble fractions. PCMB-treated cells accumulated more 67Cu, but less
than 10% was bound to the particulate (membrane) fraction. Pb also
increased 67Cu accumulation without affecting Km and Vmax of 67Cu
uptake. These data suggest carriers for import and export of Cu in C6
cells are distinct or operate in two different cellular environments.
Efflux is a sulfhydryl-dependent process subject to inhibition by Pb.
The data are consistent with a P-type ATPase in the efflux of Cu from
cells and the potential for Pb to inhibit the efflux mechanism.
Received 17 November 1994; accepted in final form 3 May 1995.
APS Manuscript Number C674-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 16 May 1995.