Differential effects of nitric oxide and cyclo-oxygenase inhibition on the diameter of porcine retinal vessels with different caliber during hypoxia ex vivo

Jensen, Peter Kryger; Aalkjær, Christian; Bek, Toke

doi:10.1016/j.exer.2017.04.001

Cited by 10 publications

(4 citation statements)

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“…A similar threshold has been found in the cerebral circulation 28 and implies that minor fluctuations in the arterial blood pressure are transmitted to the precapillary arterioles that regulate recruitment and intermittency of blood flow in the microvascular units. 29 A prominent role of these smaller vessels for regulating retinal blood flow is consistent with observations in vitro 5,6,[30][31][32] and with vivo findings that increased metabolism, resulting in a 3% to 4% dilatation of the larger retinal arterioles, elicits an approximately 10 times higher increase in retinal blood flow. 4,33 In the present study, the increased arterial blood pressure can be expected to have been transmitted to the macular microcirculation since no adaptive changes were observed in diameter and oxygen saturation in the larger vessels to this area.…”

Section: Discussionsupporting

confidence: 83%

“…1,2 However, evidence suggests that the smaller vessels also play a significant role in this regulation. [3][4][5][6] In the macular area, vessel diameters and flow have been studied in perifoveal capillaries, 7,8 whereas less evidence has been obtained about the extrafoveal microcirculation. 9,10 Smaller retinal vessels outside the macular area are difficult to study, but the relevance of also investigating blood flow in this zone is testified by observations of differences in diameter regulation, 11 oxygen saturation, 12 and ischemic conditioning 13 in vessels supplying the macular area and the retinal periphery.…”

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confidence: 99%

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Reduced Oxygen Extraction in the Retinal Periphery When the Arterial Blood Pressure Is Increased by Isometric Exercise in Normal Persons

Bek

Jeppesen

2021

Invest. Ophthalmol. Vis. Sci.

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Section: Discussionsupporting

confidence: 83%

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confidence: 99%

Reduced Oxygen Extraction in the Retinal Periphery When the Arterial Blood Pressure Is Increased by Isometric Exercise in Normal Persons

Bek

Jeppesen

2021

Invest. Ophthalmol. Vis. Sci.

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“…This blood-pressure driven change has been shown in vivo in the retina [ 15 – 17 ], where a systolic rise of 15–20 mmHg led to a reactive vasoconstriction. It is assumed that this response is mainly driven by endothelial cells and other local mediators (oxygen, carbon dioxide, angiotensin-II, adenosine, nitric oxide, endothelin-1) [ 37 ].…”

Section: Discussionmentioning

confidence: 99%

The assessment of acute chorioretinal changes due to intensive physical exercise in young adults

et al. 2022

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Purpose There is abundant evidence on the benefits of physical activity on cardiovascular health. However, there are only few data on the acute effects of physical exercise on the retina and choroid. Our aim was the in vivo examination of chorioretinal alterations following short intense physical activity by spectral domain optical coherence tomography (SD-OCT). Methods Twenty-one eyes of 21 healthy, young subjects (mean age 22.5 ± 4.1 years, 15 males and 6 females) were recruited. Macular scanning with a SD-OCT was performed before and following a vita maxima-type physical strain exercise on a rowing ergometer until complete fatigue. Follow-up OCT scans were performed 1, 5, 15, 30 and 60 minutes following the exercise. The OCT images were exported and analyzed using our custom-built OCTRIMA 3D software and the thickness of 7 retinal layers was calculated, along with semi-automated measurement of the choroidal thickness. One-way ANOVA analysis was performed followed by Dunnett post hoc test for the thickness change compared to baseline and the correlation between performance and thickness change has also been calculated. The level of significance was set at 0.001. Results We observed a significant thinning of the total retina 1 minute post-exercise (-7.3 ± 0.6 μm, p < 0.001) which was followed by a significant thickening by 5 and 15 minutes (+3.6 ± 0.6 μm and +4.0 ± 0.6 μm, respectively, both p <0.001). Post-exercise retinal thickness returned to baseline by 30 minutes. This trend was present throughout the most layers of the retina, with significant changes in the ganglion cell–inner plexiform layer complex, (-1.3 ± 0.1 μm, +0.6 ± 0.1 μm and +0.7 ± 0.1 μm, respectively, p <0.001 for all), in the inner nuclear layer at 1 and 5 minutes (-0.8 ± 0.1 μm and +0.8 ± 0.1 μm, respectively, p <0.001 for both), in the outer nuclear layer–photoreceptor inner segment complex at 5 minute (+2.3 ± 0.4 μm, p <0.001 for all) and in the interdigitation zone–retinal pigment epithelium complex at 1 and 15 minutes (-3.3 ± 0.4 μm and +1.8 ± 0.4 μm, respectively, p <0.001 for both). There was no significant change in choroidal thickness; however, we could detect a tendency towards thinning at 1, 15, and 30 minutes following exercise. The observed changes in thickness change did not correlate with performance. Similar trends were observed in both professional and amateur sportsmen (n = 15 and n = 6, respectively). The absolute changes in choroidal thickness did not show any correlation with the thickness changes of the intraretinal layers. Conclusions Our study implies that in young adults, intense physical exercise has an acute effect on the granular layers of the retina, resulting in thinning followed by rebound thickening before normalization. We could not identify any clear correlation with either choroidal changes or performance that might explain our observations, and hence the exact mechanism warrants further clarification. We believe that a combination of vascular and mechanic changes is behind the observed trends.

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“…10 Recently, attention has been directed at different effects of intra-and extravascular application of vasoactive compounds 11 and the role of pre-capillary arterioles and capillaries for regulating retinal blood flow. [12][13][14] However, the effects of different routes of application of ATP and the role of the compound for the diameter regulation of smaller retinal vessels have not been studied in detail.…”

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Differential Effects of Intra- and Extravascular ATP on the Diameter of Porcine Vessels at Different Branching Levels Ex Vivo

Ernst

Jensen

Aalkjær

et al. 2020

Invest. Ophthalmol. Vis. Sci.

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PURPOSE. Adenosine triphosphate (ATP) is involved in the diameter regulation of retinal vessels. The compound has been shown to induce both constriction and dilatation, but the detailed mechanisms underlying these effects and the site of action of the compound are not known in detail. Therefore, the purpose of the present study was to investigate whether the vasoactive effects of ATP on retinal vessels depend on intra-and extravascular application, and to study whether the effects differ at different vascular branching levels. METHODS. Diameter changes in arterioles, pre-capillary arterioles, and capillaries were studied in perfused porcine hemiretinas (n = 48) ex vivo after intra-and extravascular application of the nondegradable ATP analogue ATP-γ-S or ATP in the presence or not of antagonists to the CD73/ecto-5-nucleotidase (AOPCP), the P2-purinergic receptor (PPADS), the A3-adenosine receptor (MRS1523), and the synthesis of cyclooxygenase products (ibuprofen). RESULTS. Intravascular ATP-induced constriction and extravascular ATP-induced dilatation of retinal arterioles, pre-capillary arterioles and capillaries, and dilatation was inhibited by ibuprofen. Both constriction and dilatation of arterioles were inhibited by antagonizing ATP degradation. Furthermore, constriction at all three branching levels was antagonized by blocking the A3 purinoceptor, whereas constriction in arterioles and pre-capillary arterioles was antagonized by blocking the P2 purinoceptor. CONCLUSIONS. ATP affects the diameter of retinal arterioles, pre-capillary arterioles, and capillaries through different pathways, and the effects depend on whether the compound is administered intravascularly or extravascularly. This may form the basis for selective interventions on retinal vascular disease with differential involvement of vessels at different branching levels.

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Differential effects of nitric oxide and cyclo-oxygenase inhibition on the diameter of porcine retinal vessels with different caliber during hypoxia ex vivo

Cited by 10 publications

References 39 publications

Reduced Oxygen Extraction in the Retinal Periphery When the Arterial Blood Pressure Is Increased by Isometric Exercise in Normal Persons

Reduced Oxygen Extraction in the Retinal Periphery When the Arterial Blood Pressure Is Increased by Isometric Exercise in Normal Persons

The assessment of acute chorioretinal changes due to intensive physical exercise in young adults

Differential Effects of Intra- and Extravascular ATP on the Diameter of Porcine Vessels at Different Branching Levels Ex Vivo

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