Protein kinase C effects on nerve function, perfusion, Na(+), K(+)-ATPase activity and glutathione content in diabetic rats.
OBJECTIVE
Increased protein kinase C activity has been linked to diabetic vascular complications in the retina and kidney, which were attenuated by protein kinase C antagonist treatment. Neuropathy has a vascular component, therefore, the aim was to assess whether treatment with WAY151 003 or chelerythrine, inhibitors of protein kinase C regulatory and catalytic domains respectively, could correct nerve blood flow, conduction velocity, Na(+),K(+)-ATPase, and glutathione deficits in diabetic rats.


METHODS
Diabetes was induced by streptozotocin. Sciatic nerve conduction velocity was measured in vivo and sciatic endoneurial perfusion was monitored by microelectrode polarography and hydrogen clearance. Glutathione content and Na(+),K(+)-ATPase activity were measured in extracts from homogenised sciatic nerves.


RESULTS
After 8 weeks of diabetes, sciatic blood flow was 50 % reduced. Two weeks of WAY151 003 (3 or 100 mg/kg) treatment completely corrected this deficit and chelerythrine dose-dependently improved nerve perfusion. The inhibitors dose-dependently corrected a 20 % diabetic motor conduction deficit, however, at high doses ( > 3.0 mg/kg WAY151003; > 0.1 mg/kg chelerythrine) conduction velocity was reduced towards the diabetic level. Sciatic Na(+),K(+)-ATPase activity, 42 % reduced by diabetes, was partially corrected by low but not high dose WAY151 003. In contrast, only a very high dose of chelerythrine partially restored Na(+),K(+)-ATPase activity. A 30 % diabetic deficit in sciatic glutathione content was unchanged by protein kinase C inhibition. The benefits of WAY151 003 on blood flow and conduction velocity were blocked by nitric oxide synthase inhibitor co-treatment.


CONCLUSIONS
Protein kinase C contributes to experimental diabetic neuropathy by a neurovascular mechanism rather than through Na(+),K(+)-ATPase defects.
Cameron
N E
NE
Department of Biomedical Sciences, University of Aberdeen, Aberdeen, Scotland, UK.
Cotter
M A
MA
Jack
A M
AM
Basso
M D
MD
Hohman
T C
TC
D000470:Alkaloids; D000818:Animals; D053119:Benzophenanthridines; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism / Q000503:physiopathology*; D003929:Diabetic Neuropathies / Q000188:drug therapy / Q000503:physiopathology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008297:Male; D009431:Neural Conduction / Q000187:drug effects / Q000502:physiology; D010617:Phenanthridines / Q000494:pharmacology*; D010880:Piperidines / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow / Q000187:drug effects; D012584:Sciatic Nerve / Q000098:blood supply / Q000187:drug effects / Q000503:physiopathology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D000470:Alkaloids; D053119:Benzophenanthridines; D004791:Enzyme Inhibitors; D010617:Phenanthridines; D010880:Piperidines; C069701:NPC 15437; C016299:chelerythrine; D011493:Protein Kinase C; D000254:Sodium-Potassium-Exchanging ATPase