Aldose reductase inhibition, nerve perfusion, oxygenation and function in streptozotocin-diabetic rats: dose-response considerations and independence from a myo-inositol mechanism.
We examined the effects of aldose reductase inhibition on nerve biochemistry and function, blood flow and endoneurial oxygenation in experimental diabetes mellitus. After 1 month untreated diabetes in rats, treatment with the novel sulphonylnitromethane aldose reductase inhibitor, ZENECA ZD5522, prevented a progressive increase in sciatic nerve resistance to hypoxic conduction failure (p < 0.05). Motor conduction velocity deficits after 4 months untreated diabetes were rapidly returned to normal within 12 days (p < 0.0001) by ZD5522 treatment. Following 2-months untreated diabetes, examination of 1 month ZD5522 treatment dose-response relationships for correction of nerve sorbitol and fructose accumulations and reduction in myo-inositol concentration, sciatic motor and saphenous sensory conduction velocity and sciatic blood flow by laser-Doppler flowmetry revealed poor agreement between nerve function and biochemical indices. In addition, polyol accumulation differed between sciatic and saphenous nerves, the latter showing ten-fold lower sorbitol concentrations. Laser-Doppler blood flow was 60% decreased by untreated diabetes (p < 0.001) and there was a strong correlation between ZD5522-mediated increases in blood flow and conduction velocity (p < 0.0001). Measurement of nutritive endoneurial blood flow by microelectrode polarography and hydrogen clearance showed 44% and 45% deficits for 1 and 2 months untreated diabetes (p < 0.001) that were prevented by ponalrestat and ZD5522 treatments, respectively. In contrast, 2 months myo-inositol treatment from diabetes induction did not prevent reduction in blood flow or sciatic motor conduction velocity. A 37% reduction in endoneurial oxygen tension after 2 months diabetes (p < 0.001) was completely prevented by ZD5522 treatment (p < 0.001). The data show that a very high degree of polyol pathway blockade is necessary to correct nerve functional deficits and that aldose reductase inhibitors have a neurovascular action that does not depend on restoration of nerve myo-inositol.
Cameron
N E
NE
Department of Biomedical Sciences, University of Aberdeen, Scotland, UK.
Cotter
M A
MA
Dines
K C
KC
Maxfield
E K
EK
Carey
F
F
Mirrlees
D J
DJ
D000083:Acetanilides / Q000494:pharmacology*; D000449:Aldehyde Reductase / Q000037:antagonists & inhibitors*; D000818:Animals; D001783:Blood Flow Velocity / Q000187:drug effects; D001786:Blood Glucose / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D004305:Dose-Response Relationship, Drug; D007294:Inositol / Q000378:metabolism; D008297:Male; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology; D009431:Neural Conduction / Q000187:drug effects / Q000502:physiology; D010100:Oxygen / Q000378:metabolism*; D010477:Perfusion; D010525:Peripheral Nerves / Q000098:blood supply / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000098:blood supply / Q000502:physiology*; D013450:Sulfones / Q000494:pharmacology*
D000083:Acetanilides; D001786:Blood Glucose; D013450:Sulfones; C090184:ZENECA ZD 5522; D007294:Inositol; D000449:Aldehyde Reductase; D010100:Oxygen