14. Inorganic Phosphate Flashcards
How Much Phosphate Makes up the Skeleton?
80 - 85%
How Much Phosphate is Found in the Extracellular Fluid
and in What Forms?
15% in ECF = as INORGANIC Sulphate
Intracellularly = as ORGANIC Phosphates; Phospholipids, Nucleic Acids + ATP
Which Inorganic Phosphates are PRIMARILY found in the Skeleton?
Hydroxyapatite
Calcium Phosphate
What do These Inorganic Phosphates (in Skeleton) Form?
HIGH Energy Compounds = ATP
Co-factors = NADP
What are These Inorganic Phosphates (in Skeleton) Involved in?
Intermediary Metabolism
Various Enzyme Systems = Adenylate Cyclase
What are the General Functions of Phosphate?
Muscle Contractility
Neurologic Function
Electrolyte Transport
Oxygen Carrying Hb = 2,3-DPG
What does Inorganic Phosphate Exists As in Serum?
Divalent Anion= (HPO4)2-
Monovalent Anion = (H2PO4)-
- Which are IMPORTANT BUFFERS!
Which Form of Phosphate is ONLY Measured in Routine Clinical Practice?
Inorganic Phosphate
Where is Blood Phosphate Derived From?
MOSTY from Diet = 60-80% Ingested is ABSORBED in Gut, Via Passive Transport
SOME from Bone Metabolism
What Regulates the Levels of Phosphate?
PTH = LOWERING Phosphate Levels
Vitamin D + Growth Hormone = INCREASES Phosphate Levels
What is the Role of PTH in LOWERING Phosphate Levels?
INDUCES Phosphaturia
- Which is IMPAIRED Capacity to Reabsorb Phosphate
- From the Glomerular Filtrate
What is the Role of Vitamin D in INCREASING Phosphate Levels?
INCREASES Intestinal Reabsorption
INCREASED Renal Absorption
What is the Role of Growth Hormone in INCREASING Phosphate Levels?
Main Regulator of Skeletal Growth
REDUCES Renal Excretion of Phosphate - HENCE INCREASED Serum Levels
What Analytical Method is Used to Measure Phosphate?
Spectrophotometric Determination of Coloured Complex
What Reaction is Used to Determine Inorganic Phosphate?
Phosphate + Ammonium Molybdate
==> Phosphomolybdate Complex
How is Direct UV Measurement Used?
On Colourless Unreduced Complex
Absorption at 340 nm
What is the Enzymatic Method?
Phosphorous Undergoes Enzymatic Reactions
Catalyzed by
- Glycogen Phosphorylase
- Phosphoglucomutase
- Glucose-6-Phosphate Dehydrogenase
NADPH Produced can be Used for Measurement
What Type of Specimen is Preferred for Investigation of Phosporous?
Serum
As MOST Anticoagulants, EXCEPT Heparin = Interfere with Results + Show LOW Values
Which Type of Specimens are NOT ACCEPTED for Investigation of Phosphorous?
and Why?
Hemolyzed Specimens
- Erythrocytes Contain HIGH Level of Organic Esters
- Which are Hydrolysed to Inorganic Phosphate, DURING STORAGE
- HENCE Show INCREASED Value
What is the Reference Range of Phosphate in Serum?
0.89 - 1.44 mmol / l
How do Phosphate Levels Vary?
HIGH LEVELS = In Afternoon + Evening
LOW LEVELS = After Meals
What are the Causes of HYPER-Phosphatemia?
- Increased Intake
- Increased Production
- Reduced Loss
1| What are Examples of INCREASED INTAKE of Phosphate?
IV Infusion
Oral Supplementation
Vitamin D Intoxication
Acute Phosphorous Poisoning
2| What are Examples of INCREASED PRODUCTION of Phosphate?
Tumour-Lysis Syndrome
Rhabdomyolysis
Hemolysis
Acid-Base Disorders = Lactic Acidosis; Diabetic Ketoacidosis; Respiratory Acidosis
3| What REDUCES the LOSS of Phosphate?
Renal Failure
Hypoparathyroidism
Acromegaly
Tumoral Calcinosis
Vitamin D Intoxication
Bisphosphate Therapy
Magnesium Deficiency
Multiple Myeloma
What are the Causes of HYPOPhosphatemia?
- Inadequate Intake
- Excessive Loss
- Redistribution
1| What are Examples of INADEQUATE Intake of Phosphorus?
a. Malnutrition
b. Malabsorption
c. Agents binding with Phosphate, REDUCING Absorption
1a| Which Agents Reduces Absorption, When Bound to Phosphate?
Magnesium
Anti-acids
2| What Causes EXCESSIVE LOSS of Phosphate?
Phosphate + Osmotic Diuretics
Continuous Dialysis
Hyperglycaemia
Hyperparathyroidism
3| What Causes Redistribution of Phosphate?
SHIFT from Serum INTO Cells due to:
- Carbohydrate Infusions
- Hyperglycaemia
- Hormonal Effects = Insulin / Glucagon
