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Related Concept Videos

Hemoglobin01:24

Hemoglobin

Hemoglobin is a globular protein made up of four subunits. Two of these subunits are alpha chains, and the other two are beta chains. Each subunit contains a molecule of heme, which has an iron atom and can bind to oxygen. When an oxygen molecule binds to one heme group, it changes the shape of hemoglobin, making it easier for the other heme groups to bind oxygen as well.
When all four heme groups are bound to oxygen, the resulting molecule is called oxyhemoglobin. As a result, arterial blood...
Oxygen Transport in the Blood01:27

Oxygen Transport in the Blood

Hemoglobin (Hb) is a crucial molecule in the human body, consisting of four polypeptide chains, each bound to an iron-containing heme group. This unique structure enables hemoglobin to bind to oxygen, with each molecule capable of combining with four molecules of oxygen, leading to rapid and reversible oxygen loading. When fully loaded with oxygen, it is called oxyhemoglobin, while hemoglobin that has released oxygen is called reduced hemoglobin or deoxyhemoglobin. As hemoglobin binds oxygen,...
Regulation of Angiogenesis and Blood Supply01:24

Regulation of Angiogenesis and Blood Supply

Rapidly dividing tumors, embryos, and wounded tissues require more oxygen than usual, lowering the oxygen concentration in the blood. At low oxygen or hypoxic conditions, an oxygen-sensitive transcription factor called the hypoxia-inducible factor 1 or HIF1 is activated. HIF1 is a dimeric protein of alpha (ɑ) and beta (β) subunits.  Under optimal oxygen conditions, HIF1β is present in the nucleus while HIF1ɑ remains in the cytosol. HIF1ɑ is hydroxylated by prolyl hydroxylase and factor...
Overview of the Vascular System01:20

Overview of the Vascular System

The vascular system comprises an extensive network of arteries, capillaries, and veins. The vascular system can be broadly divided into the blood and lymphatic systems. Typically, blood vessels can be categorized into three histological regions: tunica intima, tunica media, and tunica adventitia. The tunica intima consists of a single layer of endothelial cells attached to the basal lamina. Underlying the basal lamina is a connective tissue layer and an elastic lamina that gives stability and...

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Retinal Vascular Reactivity as Assessed by Optical Coherence Tomography Angiography
07:23

Retinal Vascular Reactivity as Assessed by Optical Coherence Tomography Angiography

Published on: March 26, 2020

Haemoglobin and vascular function in the human retinal vascular bed.

Martin Ritt1, Joanna M Harazny, Stephanie Schmidt

  • 1Department of Nephrology and Hypertension, University of Erlangen-Nürnberg, Bavaria, Germany.

Journal of Hypertension
|January 23, 2013
PubMed
Summary

Higher haemoglobin levels impair retinal vascular function, reducing blood flow responses to stimuli. This study identifies haemoglobin as a key factor influencing the microcirculation in the human retina.

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Area of Science:

  • Ophthalmology
  • Vascular Biology
  • Physiology

Background:

  • Haemoglobin (Hb) is known to scavenge nitric oxide (NO).
  • Hb influences blood viscosity and microvessel dimensions, affecting microcirculatory shear stress.
  • The role of Hb in modulating retinal vascular function requires investigation.

Purpose of the Study:

  • To investigate the hypothesis that haemoglobin modulates retinal vascular function.
  • To assess the impact of haemoglobin levels on retinal capillary blood flow (RCF) responses.

Main Methods:

  • Studied 139 non-diabetic males with normal haemoglobin levels.
  • Assessed RCF response to flicker light (vasodilatation) and N-monomethyl-L-arginine (L-NMMA) infusion (vasoconstriction, basal NO activity).
  • Utilized non-invasive, in vivo scanning laser Doppler flowmetry for retinal parameter assessment.

Main Results:

  • Patients with Hb ≥ median showed reduced RCF increase to flicker light (2.83 ± 12%) and greater RCF decrease to L-NMMA (-7.35 ± 13%) compared to those below median.
  • Hb was negatively correlated with RCF percentage change during both flicker light exposure (r = -0.249, P = 0.004) and L-NMMA infusion (r = -0.201, P = 0.018).
  • Multiple regression confirmed Hb as an independent determinant of RCF response to flicker light and L-NMMA.

Conclusions:

  • Haemoglobin is an independent determinant of vascular function in the human retinal vascular bed.
  • Elevated haemoglobin levels are associated with impaired retinal vascular responsiveness.