Week 5.2 Flashcards
Potassium homeostasis (2 main regulations)
- Intake of K+
- Renal secretion & urine excretion of K+
What mainly controls K+ homeostasis
Aldosterone will respond and change K+ concentration
What are the effects of abnormal potassium levels
Plasma potassium normally controls neuron excitability:
Excessive potassium -> decreases excitability, cardiac arrythmia, muscle pain.
Low potassium -> muscle cramp (hyperaldosteronism)
What could cause hyperkalaemia (3 causes)
- Kidney’s inability to excrete K+
- ICF/ECF shifts: cell lysis
- Hormone deficiency: aldosterone insufficiency (low cell intake)
maybe intake + renal.
Hypokalemia causes
- hormone: high aldosterone levels (cell uptake)
- diarrhoea
- diuretics
- alcoholism (insufficient intake)
What could severe diarrhoea lead to (3 losses):
Loss of:
Water, Potassium, Bicarbonate
Lead to:
Loss of blood volume: sodium reabsorption, reduced GFR
Loss of potassium: potassium reabsorption from urine
Loss of bicarbonate: acidosis
Significance of ECF volume
Regulate blood pressure
Significance of ECF osmolarity
prevent cell shrinkage and swelling
what system regulates ECF volume
Renin-Angiotensin System-> Aldosterone
Sodium reabsorption/Excretion
what regulates ECF osmolarity
Water balance -> regulated by ADH
antidiuretic hormone (ADH) -> increase urine concentration (retain water)
no ADH -> dilute urine
SYNDROME OF INAPPROPRIATE ADH (what is an example)
1 example: Smoker -> lung tumour
The tumour produces ADH which leads to water retention + sodium dilution.
Other examples: Malignancies, cerebral pathologies, drugs
what is hypotonicity (concentration of sodium)
low osmolarity (low plasma sodium conc) -> water enter cells swell
what could hypotonicity cause
cerebral oedema
What is osmotic demyelination syndrome
Neurological disorder: too rapid compensatory response to hyponatraemia (low sodium in blood) - hypotonicity:
When ECF concentration gets lower than brain cell ICF during correction, cells shrink.
hypovolaemia (low BP) sensed by kidney
RAAS is activated, salt reclaimed -> increase ECF.
high BP sensed by kidney
RAAS is suppressed, salt wasted -> decrease ECF.
oedema and effective circulating volume
example 1: cardiac failure, high hydrostatic pressure
example 2: nephrotic syndrome, protein loss, low oncotic pressure
ECF expand leads to oedema.
But the body is still increasing sodium reabsorption due to the low effective circulating volume.
what causes low sodium levels (hyponatraemia)
- SIADH: water retention.
- renal failure
- Oedema
What could lead to high sodium (hypernatraemia)
- dehydration (water intake)
- dehydration due to diabetes insipidus (polyuria)
what are some analytes (examples)
drugs, hormones, electrolyte
specificity compared between mass spectrometry and immunoassay
mass spectrometry can be more specific when the antibody for immunoassays is lacking selectivity.
disadvantage of MS (mass spec.)
It is less accessible
Bland Altman Plot
different between the results of 2 assays
Bland Altman Plot when low concentration
More variability
C
Comparing MS and immunoassay in Bland Altman Plot
When immunoassay reading is always higher than MS, then there could be cross-reactivity.
Problem with testosterone with immunoassay
the antibody cross-reacts to DHEAS, therefore a higher reading in the plot
2 Main types of Mass Spec.
Gas chromatography - MS
Liquid chromatography - MS
Separation during Gas Chroma. - MS
When the analytes separate on volatility/boiling point.
Separation during Liquid Chroma. - MS
Separation according to partition coefficient:
partition coefficient: conc in oily vs conc in aqueous phase.
Column Chromatography mechanism
Stationary Phase and Mobile Phase, analytes on MP will move at different speeds.
High performance Liquid Chroma. (HPLC)
Stationary phase: Polarity changes
silica backbone and different chemical groups bound.
how to ionise volatile, small molecules?
through electron impact.
electron impact ionisation
e- impact will ionise and fragment most organic molecules.
The ion fragments will show up as different peaks on mass spectrum.
When is electron spray used?
bigger compounds (peptides…)
molecules have readily-ionisable groups
how is electron spray used
- Put molecule of interest in a charged liquid phase
- evaporate the liquid phase, only molecule of interest will be left charged.
limitation of electron spray ionisation
There will be fewer fragment ions compared to gas.
Molecule picks up multiple charges -> difficult interpretation for m/z ratio.
What is used in the final detection?
Single/Triple Quadruples
Single Quadruple
4 Poles with Adjustable charge:
the selected ion will have a stable trajectory to the detector
limited mass range (max 1000 m/z)
Triple Quadruple (steps)
first Q: selects precursor ions from sample.
second Q: collision with a gas to the ions, fragments to smaller ions.
third Q: the final/product ion will be selected.
what is a matrix
has background noise: solvent, other impurities
MS-MS compared to MS
better selectivity, less preparation, reduce background noise.
BUT: less accessible, expensive.
what is the important characteristic of the internal standard
should be an isotopomer of the analyte, should have similar chemical characteristics.
to behave similarly during separation, ionisation etc.
when is qualitative analysis used?
In drug abuse.
toxic metabolites of drugs.
example with inborn error metabolites
enzyme dysfunction: disporportionate products (steroids: aldosterone, cortisol, oestradiol…)
example with exogenous and endogenous testosterone
1.drug abuse: testosterone/epi-testosterone >6.
2. the exogenous testosterone from plants also has less C13 than human produced. (C13:12 ratio)
