The mechanism and change in the optic nerve head (ONH) circulation in rabbits after glucose loading.
OBJECTIVE
To assess the influence of the blood glucose level on ocular capillary circulation, we induced clinically significant hyperglycemia (200--300 mg/dl) in rabbits and investigated the changes in the optic nerve head (ONH) circulation.


METHODS
Hyperglycemia was induced by injection of glucose (5.6 mmol/kg) into an auricular vein of healthy albino rabbits and changes in the ONH circulation were measured by the laser speckle method. In order to examine the role of nitric oxide (NO), glucose was administered after intravenous injection of an NO synthetase inhibitor (N(G)-nitro-L-arginine methyl ester, L-NAME, 1 mg/kg), then changes in the ONH circulation were measured.


RESULTS
The blood glucose level reached a peak at 30 min after glucose loading and returned to its initial level by 2 hours. ONH circulation showed a 60% increase compared with its initial level at 15 min after glucose loading and subsequently remained almost unchanged throughout the 2-hour observation period. There were no significant changes of the blood pressure, heart rate, or intraocular pressure. The glucose-induced increase of ONH circulation was completely inhibited by pretreatment with L-NAME.


CONCLUSIONS
ONH circulation was increased by administration of glucose to healthy rabbits. A high blood glucose level seems to promote ocular capillary circulation and NO as well as insulin appear to have a role in this process.
Kida
T
T
Department of Ophthalmology, Osaka Medical College, Osaka, Japan. opt038@poh.osaka-med.ac.jp
Oku
H
H
Sugiyama
T
T
Ikeda
T
T
D000818:Animals; D001775:Blood Circulation / Q000502:physiology; D001783:Blood Flow Velocity / Q000502:physiology; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure; D004791:Enzyme Inhibitors / Q000008:administration & dosage; D006339:Heart Rate; D006943:Hyperglycemia / Q000503:physiopathology*; D007275:Injections, Intravenous; D007328:Insulin / Q000097:blood; D007429:Intraocular Pressure; D017078:Laser-Doppler Flowmetry; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage; D009569:Nitric Oxide / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D009898:Optic Disk / Q000098:blood supply*; D011817:Rabbits; D012039:Regional Blood Flow / Q000502:physiology
D001786:Blood Glucose; D004791:Enzyme Inhibitors; D007328:Insulin; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester