1 / 19

MLAB 2401: Clinical Chemistry Keri Brophy-Martinez

MLAB 2401: Clinical Chemistry Keri Brophy-Martinez. Chapter 5: Porphyrins and Hemoglobin Overview . Overview of Iron. Essential mineral to most living organisms Most abundant trace element 2-2.5 of the 3-5 grams of iron in our bodies is found in hemoglobin (RBCs and RBC precursors).

kineta
Download Presentation

MLAB 2401: Clinical Chemistry Keri Brophy-Martinez

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. MLAB 2401: Clinical ChemistryKeri Brophy-Martinez Chapter 5: Porphyrins and Hemoglobin Overview

  2. Overview of Iron • Essential mineral to most living organisms • Most abundant trace element • 2-2.5 of the 3-5 grams of iron in our bodies is found in hemoglobin (RBCs and RBC precursors)

  3. Where does iron come from? • Dietary sources - meats, especially organ meats, spinach, beats,... etc.

  4. Regulation • Dietary sources • Absorption • Must be in ferrous state (Fe++) • Occurs in the stomach/small intestines • Iron “stores” • Iron is recycled when RBCs are broken down • 25% stored in liver, spleen and bone marrow as ferritin or (Fe3+)

  5. Functions of Iron • Essential element of heme and hemoglobin • Component of methemoglobin, myoglobin and some enzymes • Cellular oxidative mechanisms

  6. Heme Sythesis Review The addition of ferrous iron (Fe++)forms heme

  7. Forms of Iron • Ferrous(Fe2+) • Absorbed form • Ferric (Fe3+) • Ferritin • Transport and storage form • Free ferric form is picked up in the plasma by protein transferrin • Delivered to cells having receptor sites • Gut mucosal cells • Liver cells • RE system cells • Once inside the cell, ferric iron attaches to protein apoferritinto form ferritin • Deficiency of apoferritin results in ferric iron deposits or hemosiderin, which is insoluble

  8. Iron Links http://www.umm.edu/blood/aneiron.htm http://www.ehendrick.org/healthy/000772.htm http://www.nlm.nih.gov/medlineplus/ency/article/000584.htm http://www.healthservices.gov.bc.ca/msp/protoguides/gps/ferritin.html

  9. Hemoglobin • Structure, Synthesis, Degradation and Role • Refer to Hematology notes for review • Chapter 6 in McKenzie text

  10. Porphyrins • General structure • Cyclic compounds called tetrapyrroles • Linked by four pyrrole rings bonded by methene bridges

  11. Porphyrins • Chemical intermediates in the synthesis of hemoglobin, myoglobin and other respiratory pigments (cytochromes) • Clinical significance • Presence indicates abnormal heme synthesis

  12. Physical properties • Color • Coloration around 405 nm • Usually red • Fluorescence • around 620 nm • Reddish-pink color • Chelation • Arrangement of nitrogen atoms allows chelation of metal atoms such as iron, that participate in oxidative metabolism

  13. Porphyrin Synthesis & Control • Synthesis • Bone marrow and liver are the main site • Some steps of synthesis occur in mitochrondria and cytoplasm of cell • Control • Enzyme: δ-aminolevulinic acid (ALA) • Found in liver • Increases in hepatic heme decrease the production of ALA • Decreases or depletions of heme result in ALA increased production • Rate of heme syntheis is flexible and can change rapidily in response to external stimuli

  14. Porphyrins: Ones to keep an Eye on • Uroporphyrin: URO • Water soluble • Heme precursor • Found in urine • Coproporphyrin: COPRO • Water soluble • Heme precursor • Found in urine and feces • Protoporphyrin: PROTO • Water insoluble • Heme precursor • Found in feces

  15. Porphyrinogens • Reduced form of porphyrins • Functional precursor of heme • Difficult to measure due to instability and colorlessness

  16. Glycated hemoglobin • Hemoglobin A 1c most stable • Indicator of long-term glucose control • Why? • Reflects sustained average plasma glucose over the RBC life span • Correlates with risk of cardiovascular disease and other vascular disorders

  17. Myoglobin • Heme protein found in skeletal and cardiac muscle • Unable to release oxygen, except under low oxygen tension • Main function is to transport oxygen from the muscle cell membrane to the mitochondria • Serves as an extra reserve of oxygen to help exercising muscle maintain activity longer • Used to diagnose acute myocardial infarction

  18. Lead • Found in the environment and in paint • Considered a toxin, plays no known role in NORMAL human physiology • Exposure primarily respiratory or gastrointestinal • Half-life in whole blood= 2-3 weeks • Half-life= the time required by the body, tissue or organ to metabolize or inactivate half the amount of substance taken in

  19. Lead • Absorption • Depends on age, nutritional status and other substances that are present • Transport • Once in the blood, 94% transferred to RBC bound to hgb • Once it reaches its half-life, lead is distributed to soft tissues, such as kidneys, liver and brain. Final storage is in soft tissue(5%) and bone (95%) • Excretion • Urine (76%) • Feces (16%) • Other (8%)

More Related