Glucose stimulates O2 consumption, NOS, and Na/H exchange in diabetic rat proximal tubules.
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 x min(-1) x mg(-1)) and oligomycin-sensitive O2 consumption (QO2; 16.0 +/- 1.7 vs. 11.3 +/- 0.7 nmol x min(-1) x mg(-1)). Ethylisopropyl amiloride-inhibitable QO2 (6.5 +/- 0.6 vs. 2.4 +/- 0.3 nmol x min(-1) x mg(-1)) accounted for increased oligomycin-sensitive QO2 in diabetic tubules. N(G)-monomethyl-L-arginine methyl ester (L-NAME) inhibited most of the increase in 86Rb uptake and QO2 in diabetic tubules. L-NAME had little effect on nondiabetic tubules. Inhibition of QO2 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 QO2 in proximal tubules.
Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada M5G 1L5. andrew.baines@utoronto.ca
Andrew
A
Baines
Patrick
P
Ho
D000584:Amiloride / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D002956:Citrulline / Q000096:biosynthesis; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D016883:Diabetic Ketoacidosis / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology*; D006943:Hyperglycemia / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III; D009840:Oligomycins / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D012414:Rubidium Radioisotopes; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D014475:Uncoupling Agents / Q000494:pharmacology
D000889:Anti-Arrhythmia Agents; D004791:Enzyme Inhibitors; D009840:Oligomycins; D012414:Rubidium Radioisotopes; D017923:Sodium-Hydrogen Exchangers; D014475:Uncoupling Agents; D002956:Citrulline; D010042:Ouabain; D000584:Amiloride; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D005947:Glucose; D019331:NG-Nitroarginine Methyl Ester; C039614:ethylisopropylamiloride