Altered vasoreactivity to angiotensin II in experimental diabetic neuropathy: role of nitric oxide.
We evaluated the effects of angiotensin II and an angiotensin-converting enzyme inhibitor (cilazapril) on nerve blood flow (NBF) and electrophysiology in control and diabetic rats. When applied locally to the sciatic nerve, the dose-response curve of angiotensin II was more potent in experimental diabetic neuropathy (EDN) than control rats. No difference existed in plasma angiotensin II levels between EDN and controls. The rats were given typical rat pellets or pellets treated with 10 mg/kg per day cilazapril for 4 weeks. Diabetes caused a significant reduction in NBF, nerve conduction velocity, and compound muscle action potential (CMAP) amplitudes. NBF was significantly increased in diabetic rats supplemented with cilazapril diet, and nerve conduction velocity and amplitudes of the CMAP were also improved after 4 weeks on this diet. Direct application 10(-3) mol/L cilazapril on sciatic nerve did not increase NBF in normal and EDN rats. We topically applied the nitric oxide synthase (NOS) inhibitor, NG-nitro-L-arginine, on sciatic nerve and observed reduced inhibition of NBF in EDN, which was correctable with a cilazapril diet. These results suggest that diabetic neuropathy may have an increasing vasopressor action with angiotensin II and this is likely to be the mechanism of NOS inhibition. Angiotensin II-converting enzyme inhibitors may have potential in the treatment of diabetic neuropathy.
Kihara
M
M
Department of Neurology, Kinki University, School of Medicine, Ohno-Higashi, Osaka-Sayama, Osaka 589, Japan.
Mitsui
M K
MK
Mitsui
Y
Y
Okuda
K
K
Nakasaka
Y
Y
Takahashi
M
M
Schmelzer
J D
JD
D000804:Angiotensin II / Q000494:pharmacology*; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology*; D000818:Animals; D017315:Cilazapril / Q000494:pharmacology*; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy* / Q000503:physiopathology; D003929:Diabetic Neuropathies / Q000188:drug therapy / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D016015:Logistic Models; D008297:Male; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow / Q000187:drug effects; D014666:Vasomotor System / Q000187:drug effects*
D000806:Angiotensin-Converting Enzyme Inhibitors; D000804:Angiotensin II; D017315:Cilazapril; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase