Influence of exercise induced hyperlactatemia on retinal blood flow during normo- and hyperglycemia.
OBJECTIVE
Short term hyperglycemia has previously been shown to induce a blood flow increase in the retina. The mechanism behind this effect is poorly understood. We set out to investigate whether exercise-induced hyperlactatemia may alter the response of retinal blood flow to hyperglycemia.


METHODS
We performed a randomized, controlled two-way cross over study comprising 12 healthy subjects, performed a 6-minutes period of dynamic exercise during an euglcaemic or hyperglycaemic insulin clamp. Retinal blood flow was assessed by combined vessel size measurement with the Zeiss retinal vessel analyzer and measurement of red blood cell velocities using bi-directional laser Doppler velocimetry. Retinal and systemic hemodynamic parameters were measured before, immediately after and 10 and 20 minutes after isometric exercise.


RESULTS
On the euglycemic study day retinal blood flow increased after dynamic exercise. The maximum increase in retinal blood flow was observed 10 minutes after the end of exercise when lactate plasma concentration peaked. Hyperglycemia increased retinal blood flow under basal conditions, but had no incremental effect during exercise induced hyperlactatemia.


CONCLUSIONS
Our results indicate that both lactate and glucose induce an increase in retinal blood flow in healthy humans. This may indicate a common pathway between glucose and lactate induced blood flow changes in the human retina.
Department of Clinical Pharmacology, University of Vienna, Austria.
Gerhard
G
Garhöfer
Andreas
A
Kopf
Elzbieta
E
Polska
Magdalena
M
Malec
Guido T
GT
Dorner
Michael
M
Wolzt
Leopold
L
Schmetterer
D000140:Acidosis, Lactic / Q000503:physiopathology*; D000328:Adult; D001783:Blood Flow Velocity; D001786:Blood Glucose / Q000502:physiology; D018592:Cross-Over Studies; D015444:Exercise / Q000502:physiology*; D005947:Glucose / Q000008:administration & dosage; D006801:Humans; D006943:Hyperglycemia / Q000503:physiopathology*; D007773:Lactates / Q000097:blood*; D017078:Laser-Doppler Flowmetry; D008297:Male; D012039:Regional Blood Flow; D012171:Retinal Vessels / Q000502:physiology*
D001786:Blood Glucose; D007773:Lactates; D005947:Glucose