Related Experiment Video
Updated: Jul 16, 2026

Isolation of Retinal Arterioles for Ex Vivo Cell Physiology Studies
Published on: July 14, 2018
Control of retinal arterial tone by a paracrine retinal relaxing factor
Nele Maenhaut1, Koen Boussery, Christophe Delaey
1Department of Physiology and Pathophysiology, Ghent University, Ghent, Belgium.
Abstract:
Retinal blood flow is regulated by local factors. In vitro bioassay experiments give evidence that retinal tissue from different species (dogs, pigs, sheep, cows, rats, and mice) continuously releases a factor lowering tone of isolated retinal arteries. This factor is a general relaxant as it was effective in relaxing different types of vascular as well as nonvascular smooth muscle preparations. This factor is called the retinal relaxing factor (RRF) and its characteristics do not correspond with those of the many well-known vasorelaxants found in retina (i.e., NO, prostanoids, adenosine, ADP, ATP, lactate, glutamate, GABA, taurine, adrenomedullin, CGRP, ANP, BNP, and CNP). This unknown RRF is transferable, hydrophilic, and heat-stable. Its relaxing effect is independent of the presence of the vascular endothelium and of NO-synthase, adenylyl cyclase, guanylyl cyclase, and cyclooxygenase activity. RRF might have a role in hypoxic vasodilation in retinal arteries since hypoxia induces relaxation only when retinal tissue is present. Thus, the RRF pathway is sensitive to changes in oxygen tension and might be a sensitive mechanism for adjusting vascular diameter to retinal oxygen levels. Diminished RRF release might explain the decreased retinal circulation observed in disease with atrophic retina.
Related Concept Videos
Autoregulation of Blood Flow
Chemical Signaling in Autoregulation
Chemical signaling operates at the precapillary sphincter level, inciting either contraction or relaxation.
Neural Regulation of Blood Pressure
Baroreceptor Reflex
Baroreceptors, located in the carotid sinuses and aortic arch, detect changes in blood pressure. When blood pressure rises, these stretch-sensitive receptors...
The Parasympathetic Nervous System
Direct-Acting Cholinergic Agonists: Pharmacological Actions
The Retina
Paracrine Signaling

