title: Control of retinal arterial tone by a paracrine retinal relaxing factor.
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.
authors: Department of Physiology and Pathophysiology, Ghent University, Ghent, Belgium.
authors: Nele
authors: N
authors: Maenhaut
authors: Koen
authors: K
authors: Boussery
authors: Christophe
authors: C
authors: Delaey
authors: Johan
authors: J
authors: Van de Voorde
mesh_terms: D000818:Animals; D006801:Humans; D019899:Paracrine Communication / Q000502:physiology*; D012161:Retinal Artery / Q000502:physiology*; D012164:Retinal Diseases / Q000378:metabolism / Q000503:physiopathology*; D014664:Vasodilation / Q000502:physiology*; D014665:Vasodilator Agents / Q000378:metabolism*
chemical_list: D014665:Vasodilator Agents