Regulation of uveal and retinal blood flow in STZ-diabetic and non-diabetic rats; involvement of nitric oxide.
OBJECTIVE
In experimental and human diabetes mellitus evidence for an impaired function of the vascular endothelial cells has been found. The purpose of the present experiments was to measure uveal and retinal blood flow and vascular resistance at an early stage of experimental diabetes mellitus and to evaluate the effects of acetylcholine and L-arginine in control and L-NAME-pretreated animals.


METHODS
The radioactively labelled microsphere method was applied to normal Sprague-Dawley rats and rats with STZ-induced diabetes of three weeks duration.


RESULTS
In the present study, similar blood flow and vascular resistance were observed in the uvea of normal and STZ-diabetic rats. Evidence for a basal vasodilating NO-tone was found both in the uvea and in the retina of both groups. In the normal rats as well as in the diabetic animals, acetylcholine induced choroidal vasodilation. Local blood flow increased from 54 +/- 17 to 142 +/- 32 mg x min(-1) in normal rats and from 57 +/- 18 to 112 +/- 23 mg x min(-1) in diabetic rats (P < 0.05 respectively). No hemodynamic changes were observed in the anterior uvea, demonstrating a difference in reactivity between these vascular beds. In animals pretreated with the NO-synthase inhibitor L-NAME, acetylcholine did not significantly affect local blood flow in the choroid, suggesting NO as a mediator of the vasodilation.


CONCLUSIONS
The results indicate a normal action of NO in the ocular vascular beds at this stage of experimental diabetes mellitus in the rat.
Granstam
E
E
Department of Neuroscience/Ophthalmology, University Hospital, Uppsala, Sweden. Elisabeth.Granstam@ogon.uu.se
Granstam
S O
SO
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001120:Arginine / Q000494:pharmacology; D001783:Blood Flow Velocity / Q000187:drug effects; D002829:Choroid / Q000098:blood supply; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow; D012171:Retinal Vessels / Q000502:physiology*; D014602:Uvea / Q000098:blood supply* / Q000503:physiopathology; D014655:Vascular Resistance; D014664:Vasodilation / Q000187:drug effects
D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D001120:Arginine; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester