Influence of blood flow on arteriolar wall-to-lumen ratio in the human retinal circulation in vivo.
OBJECTIVE
We hypothesized that blood flow impacts on arteriolar wall-to-lumen ratio and that vasodilatory capacity is negatively related to arteriolar wall-to-lumen ratio in the human retinal vascular bed.


METHODS
The study cohort comprised 141 non-diabetic untreated male patients with (n=52) or without (n=89) arterial hypertension but without evidence for cardiovascular disease. Retinal capillary blood flow (RCF) before and after exposure to flicker light and to infusion of nitric oxide (NO) synthase inhibitor N-monomethyl-L-arginine (L-NMMA), and parameters of retinal arteriolar morphology, e.g. wall-to-lumen ratio, were assessed non-invasively and in vivo by scanning laser Doppler flowmetry.


RESULTS
The study cohort was grouped according to the median RCF into two groups. Patients with RCF above the median revealed lower wall-to-lumen ratio (0.30 ± 0.1 vs 0.34 ± 0.1 (-), P adjusted=0.023) compared to patients with RCF equal or below the median. In addition, RCF was negatively related to wall-to-lumen ratio independently of cardiovascular risk factors (ß=-0.224, P=0.026). In parallel, the decrease of RCF to L-NMMA infusion was greater in patients with RCF above the median compared to the counter group (-8.95 ± 11 vs. 0.35 ± 15 (%), P adjusted <0.001). The increase in RCF to flicker light exposure was negatively related to wall-to-lumen ratio in hypertensive but not in normotensive or all patients (r=-0.292, P=0.047, r=-0.035, P=0.746 and r=-0.126, P=0.144, respectively).


CONCLUSIONS
In the retinal circulation blood flow impacts on arteriolar wall-to-lumen ratio. Basal NO activity might modulate blood flow and arteriolar morphological changes. In hypertensive, but not in normotensive patients, the vasodilatory capacity is negatively related to arteriolar wall-to-lumen ratio in the human retinal vascular bed.
Department of Nephrology and Hypertension, University of Erlangen-Nürnberg, Erlangen, Germany.
Martin
M
Ritt
Joanna M
JM
Harazny
Christian
C
Ott
Ulrike
U
Raff
Marina
M
Lehmann
Georg
G
Michelson
Roland E
RE
Schmieder
D000328:Adult; D001160:Arterioles / Q000473:pathology / Q000503:physiopathology; D001783:Blood Flow Velocity; D002196:Capillaries / Q000473:pathology / Q000503:physiopathology; D016022:Case-Control Studies; D004791:Enzyme Inhibitors / Q000008:administration & dosage; D005858:Germany; D006801:Humans; D006973:Hypertension / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D007262:Infusions, Intravenous; D017078:Laser-Doppler Flowmetry; D008027:Light; D016014:Linear Models; D008297:Male; D008833:Microcirculation / Q000187:drug effects; D008875:Middle Aged; D015999:Multivariate Analysis; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D010775:Photic Stimulation; D012039:Regional Blood Flow; D012171:Retinal Vessels / Q000187:drug effects / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D018570:Risk Assessment; D012307:Risk Factors; D014664:Vasodilation / Q000187:drug effects; D019323:omega-N-Methylarginine / Q000008:administration & dosage
D004791:Enzyme Inhibitors; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase