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Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada M5G 1L5
Endothelial
nitric oxide synthase (NOS) and neuronal NOS protein increased in
proximal tubules of acidotic diabetic rats 3-5 wk after
streptozotocin injection. NOS activity (citrulline production) was
similar in nondiabetic and diabetic tubules incubated with low glucose
(5 mM glucose + 20 mM mannitol); but after 30 min with high
glucose (25 mM), Ca-sensitive citrulline production had increased 23%
in diabetic tubules. Glucose concentration did not influence citrulline
production in nondiabetic tubules. High glucose increased
carboxy-2-phenyl-4,4,5,5,-tetramethylimidazoline 1-oxyl-3-oxide
(cpt10)-scavenged NO sevenfold in a suspension of diabetic tubules but
did not alter NO in nondiabetic tubules. Diabetes increased
ouabain-sensitive 86Rb uptake (141 ± 9 vs. 122 ± 6 nmol · min
1 · mg
1) and
oligomycin-sensitive O2 consumption
(
O2; 16.0 ± 1.7 vs. 11.3 ± 0.7 nmol · min
1 · mg
1).
Ethylisopropyl amiloride-inhibitable
O2
(6.5 ± 0.6 vs. 2.4 ± 0.3 nmol · min
1 · mg
1)
accounted for increased oligomycin-sensitive
O2 in diabetic tubules.
NG-monomethyl-L-arginine methyl
ester (L-NAME) inhibited most of the increase in
86Rb uptake and
O2 in
diabetic tubules. L-NAME had little effect on
nondiabetic tubules. Inhibition of
O2 by
ethylisopropyl amiloride and L-NAME was only 5-8%
additive. Uncontrolled diabetes for 3-5 wk increases NOS protein
in proximal tubules and makes NOS activity sensitive to glucose
concentration. Under these conditions, NO stimulates Na-K-ATPase and
O2 in proximal tubules.
oxygen consumption; nitric oxide synthase; sodium-hydrogen exchange; kidney; streptozotocin; oligomycin; ouabain; rubidium uptake; ketoacidosis; NG-monomethyl-L-arginine methyl ester; ethylisopropyl amiloride
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