Effect of Acidosis on Isolated Porcine Retinal Vessels

Hessellund, Anders; Aalkjær, Christian; Bek, Toke

doi:10.1080/02713680600681236

Cited by 19 publications

(14 citation statements)

References 32 publications

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“…Acidosis-induced relaxation of tone in preconstricted isolated porcine retinal arterioles is associated with a hyperpolarization and a decrease in [Ca 2+ ] i in the smooth muscle cells. The same study demonstrated that the vascular response to normocapnic and hypercapnic acidosis was similar, hence independent of CO 2 , and not mediated by NO (Hessellund et al, 2006). In isolated rat retinae, pharmacological inhibition of carbonic anhydrase, resulting in extracellular acidification, is associated with an increase in capillary diameter (Reber et al, 2003).…”

Section: Regulation Of Retinal Blood Flowmentioning

confidence: 86%

Cellular and physiological mechanisms underlying blood flow regulation in the retina and choroid in health and disease

Kur

Newman

Chan‐Ling

2012

Progress in Retinal and Eye Research

541

455

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We review the cellular and physiological mechanisms responsible for the regulation of blood flow in the retina and choroid in health and disease. Due to the intrinsic light sensitivity of the retina and the direct visual accessibility of fundus blood vessels, the eye offers unique opportunities for the non-invasive investigation of mechanisms of blood flow regulation. The ability of the retinal vasculature to regulate its blood flow is contrasted with the far more restricted ability of the choroidal circulation to regulate its blood flow by virtue of the absence of glial cells, the markedly reduced pericyte ensheathment of the choroidal vasculature, and the lack of intermediate filaments in choroidal pericytes. We review the cellular and molecular components of the neurovascular unit in the retina and choroid, techniques for monitoring retinal and choroidal blood flow, responses of the retinal and choroidal circulation to light stimulation, the role of capillaries, astrocytes and pericytes in regulating blood flow, putative signaling mechanisms mediating neurovascular coupling in the retina, and changes that occur in the retinal and choroidal circulation during diabetic retinopathy, age-related macular degeneration, glaucoma, and Alzheimer's disease. We close by discussing issues that remain to be explored.

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Section: Regulation Of Retinal Blood Flowmentioning

confidence: 86%

Cellular and physiological mechanisms underlying blood flow regulation in the retina and choroid in health and disease

Kur

Newman

Chan‐Ling

2012

Progress in Retinal and Eye Research

541

455

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“…In previous studies of the effect of prostaglandins on retinal vascular tone, initial contraction was induced by the thromboxane analogue U46619 (Holmgaard et al. 2008; Holmgaard & Bek 2010), as this compound can induce a reproducible concentration‐dependent vasocontraction in these vessels (Hessellund et al. 2006).…”

Section: Discussionmentioning

confidence: 99%

Dual effect of prostaglandins on isolated intraocular porcine ciliary arteries

Kringelholt

Simonsen

Bek

2012

Acta Ophthalmologica

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ABSTRACT.Purpose: Prostaglandin analogues are used to reduce the intraocular pressure (IOP) in glaucoma, but also affect the tone of the arteries supplying the ciliary body. Previously, the effect of prostaglandins has been studied on the extraocular ciliary arteries, whereas the effect on intraocular ciliary arteries has not been studied in detail. Methods: Intraocular long posterior porcine ciliary arteries were isolated and mounted in a myograph system for isometric tension recording, and the effects of PGF 2a , the prostaglandin analogue latanoprost, PGD 2 , PGE 2 , PGI 2 and the thromboxane analogue U46619 were studied in the presence and absence of selective receptor antagonists. Results: The prostaglandins PGD 2 and PGE 2 induced relaxation at low concentrations (10 )9 -3 · 10 )7 m), which could be inhibited by blocking either the DP or the EP 4 receptor, whereas PGD 2 , PGE 2 , PGF 2a , latanoprost and U46619 induced contraction at high concentrations (10 )6 -10 )5 m), which could be inhibited by blocking the TP receptor. Additionally, blocking of the FP receptor induced a right-shift of latanoprost-induced contraction. Conclusions: Prostaglandins with affinity to DP 1 and EP 4 receptors induce relaxation at low concentrations, and prostaglandins with affinity to TP and FP receptors induce contraction at high concentrations of intraocular porcine ciliary vessels in vitro. The findings may contribute to understanding the regulation of blood flow to the ciliary body.

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“…The study showed that in addition to KPSS, also endothelin‐1 and the thromboxane analogue U46619, but not NA, could constrict porcine retinal arterioles. U46619 induced a smaller constriction than endothelin‐1 and KPSS, whereas wire myograph studies have shown a large arteriolar contraction of all three compounds in porcine and bovine retinal arterioles (Delaey & Van de Voorde 1998; Hessellund et al. 2006; Holmgaard et al.…”

Section: Discussionmentioning

confidence: 98%

“…2008). The blood flow is determined by the arteriovenous pressure difference and the vessel diameter in the vascular system, but due to methodological limitations both in vitro and in vivo studies of diameter changes have hitherto largely been performed on retinal vessels with a diameter larger than approximately 100 μm (Delaey & Van de Voorde 2000; Hessellund et al. 2006; Torring et al.…”

Section: Introductionmentioning

confidence: 99%

“…Disturbances in the retinal blood flow are involved in a number of visionthreatening diseases such as diabetic retinopathy, primary open-angle glau-coma and age-related macular degeneration (Sato et al 2006;Gardiner et al 2007;Gilmore et al 2007;Mozaffarieh et al 2008). The blood flow is determined by the arteriovenous pressure difference and the vessel diameter in the vascular system, but due to methodological limitations both in vitro and in vivo studies of diameter changes have hitherto largely been performed on retinal vessels with a diameter larger than approximately 100 lm (Delaey & Van de Voorde 2000;Hessellund et al 2006;Torring et al 2009;Heitmar et al 2010;Tilma & Bek 2012). Previous investigations have shown that the diameter of the small arterioles is also important for the regulation of blood flow (Kur et al 2012) and that the diameter regulation of these vessels may differ from that of the larger arterioles (Kuo et al 1995;de Wit et al 1998;Yamanishi et al 2006;Tevald et al 2011).…”

Section: Introductionmentioning

confidence: 99%

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Constriction of porcine retinal arterioles induced by endothelin‐1 and the thromboxane analogue U46619 in vitro decreases with increasing vascular branching level

Torring

Aalkjær

Bek

2013

Acta Ophthalmologica

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ABSTRACT.Purpose: The retinal blood flow depends on the diameter of retinal arterioles, but diameter changes in these vessels have hitherto only been assessed in vessels larger than approximately 100 lm. Therefore, a new method was developed for studying diameter changes along the vascular tree of arterioles in whole perfused segments of porcine retinas, and the effect of known vasoconstrictors on the diameter of retinal arterioles at different branching levels were studied. Methods: Thirty-four whole-mounted porcine retinas were placed in a specially designed tissue chamber. On the basis of video recordings through an inverted microscope, the diameter of retinal arterioles was measured at five different branching levels before and after addition of a high potassium concentration, or increasing concentrations of endothelin-1, the prostaglandin analogue U46619, noradrenaline or none (time controls). Results: The baseline diameter ranged from 136 lm (95% CI 132-140 lm) for 1st order arterioles to 33 lm (95% CI 21-44 lm) for 5th order arterioles. In 1st order arterioles, endothelin produced 56.6% (95% CI 47.6-64.0) and U46619 14.6% (95% CI 5.7-22.6) relative constriction compared with baseline, which for both compounds decreased significantly with increasing branching level (p < 0.0001 and p < 0.0001, respectively). The change in diameter during addition of noradrenaline did not differ significantly from the time controls (p = 0.07). Conclusions: The effect of retinal vasoconstrictors differs among larger and smaller arterioles. The study highlights the need for investigating diameter regulation in smaller retinal arterioles as a basis for understanding normal and pathological changes in retinal blood flow.

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Effect of Acidosis on Isolated Porcine Retinal Vessels

Abstract: Acidosis-induced relaxation of the tone in preconstricted isolated porcine retinal arterioles is associated with a decrease in intracellular calcium and a hyperpolarization of the smooth muscle cells. The acidosis-induced relaxation is independent of CO(2) and is not mediated through NO.

Cited by 19 publications

References 32 publications

Cellular and physiological mechanisms underlying blood flow regulation in the retina and choroid in health and disease

Cellular and physiological mechanisms underlying blood flow regulation in the retina and choroid in health and disease

Dual effect of prostaglandins on isolated intraocular porcine ciliary arteries

Constriction of porcine retinal arterioles induced by endothelin‐1 and the thromboxane analogue U46619 in vitro decreases with increasing vascular branching level

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