Increased cytosolic free sodium in platelets from patients with early-stage chronic renal failure.
Cytosolic free sodium concentration ([Na+]i) and sodium transport systems were measured in intact platelets from 19 patients with early-stage chronic renal failure and 33 healthy control subjects using the novel fluorescent dye sodium-binding-benzofuran-isophthalate. Resting [Na+]i was significantly greater in patients with chronic renal failure compared to control subjects (40.8 +/- 3.1 mmol/l versus 32.2 +/- 2.0 mmol/l, mean +/- SEM, P < 0.05). After inhibition of Na-K-ATPase by 1 mmol/l ouabain a higher net sodium influx was observed in platelets from patients with chronic renal failure compared to control subjects (49.8 +/- 8.7 mmol/l versus 28.5 +/- 5.2 mmol/l, P < 0.05). The platelet Na-H exchanger was similar in the two groups. Cytosolic free calcium concentration ([Ca2+]i) was measured using fura2 and did not show significant differences between the two groups. To evaluate whether a circulating factor may be associated with elevated [Na+]i, a linked-enzyme Na-K-ATPase assay was included. Compared to control subjects plasma from patients with chronic renal failure produced a significant inhibition of steady-state Na-K-ATPase activity by 11.2 +/- 3.0% (P < 0.01). It is concluded that early-stage renal failure is associated with significant impairment of platelet sodium metabolism.
Tepel
M
M
Medizinische Universitäts-Poliklinik, University of Münster, Germany.
Bauer
S
S
Kegel
M
M
Raffelsiefer
A
A
Wischniowski
H
H
Zidek
W
W
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001792:Blood Platelets / Q000378:metabolism*; D002352:Carrier Proteins / Q000032:analysis; D003600:Cytosol / Q000378:metabolism; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D012964:Sodium / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger; D017923:Sodium-Hydrogen Exchangers / Q000032:analysis; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D002352:Carrier Proteins; D019831:Sodium-Calcium Exchanger; D017923:Sodium-Hydrogen Exchangers; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase