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1 Department of Physiology, Monash University, Victoria 3800, Australia; 2 Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461; and 3 Physiological Laboratory, University of Cambridge, Cambridge CB2 3EG, United Kingdom
The ATPase activity of the plasma membrane Ca2+ pump
(PMCA) has been reported to be inhibited by exposure of red blood cell (RBC) PMCA preparations to high glucose concentrations. It has been
claimed that this effect could have potential pathophysiological relevance in diabetes. To ascertain whether high glucose levels also
affect PMCA transport function in intact RBCs, Ca2+
extrusion by the Ca2+-saturated pump [PMCA maximal
velocity (Vmax)] was measured in human
and rat RBCs exposed to high glucose in vivo or in vitro. Preincubation
of normal human RBCs in 30-100 mM glucose for up to 6 h had
no effect on PMCA Vmax. The mean
Vmax of RBCs from 15 diabetic subjects of
12.9 ± 0.7 mmol · 340 g
Hb
1 · h
1 was not significantly
different from that of controls (14.3 ± 0.5 mmol · 340 g Hb
1 · h
1).
Similarly, the PMCA Vmax of RBCs from 11 streptozotocin-diabetic rats was not affected by plasma glucose
levels more than three times normal for 6-8 wk. Thus exposure to
high glucose concentrations does not affect the ability of intact RBCs
to extrude Ca2+.
plasma membrane calcium pump; glycation; diabetes mellitus; streptozotocin
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