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 (86)Rb uptake (141 +/- 9 vs. 122 +/- 6 nmol.min(-1).mg(-1)) and oligomycin-sensitive O(2) consumption ((Q) over dot O(2); 16.0 +/- 1.7 vs. 11.3 +/- 0.7 nmol.min(-1).mg(-1)). Ethylisopropyl amiloride-inhibitable (Q) over dot O(2) (6.5 +/- 0.6 vs. 2.4 +/- 0.3 nmol.min(-1).mg(-1)) accounted for increased oligomycin-sensitive (Q) over dot O(2) in diabetic tubules. N(G)-monomethyl- L-arginine methyl ester (L-NAME) inhibited most of the increase in (86)Rb uptake and (Q) over dot O(2) in diabetic tubules. L-NAME had little effect on nondiabetic tubules. Inhibition of (Q) over dot O(2) 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 (Q) over dot O(2) in proximal tubules.