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Sferocytosis is a AD disease, spectrin defect; my Q is why the RBCs have an increased osmolar fragility because the conc for destruction is 0.65% (normal cells are destroyed by 0.5% NaCl);I thougth is reversed.


sinc the problem is with the membran. and osmotic fragility determine at what concentration cells that is spherocytes will lyse. spherocytes have resistent membrane so it takes higher concetration of NACL to lyse them and that corresponds with higher somotic fragility.


Tx; finally I undestood.


I thought the sperocytes are prone for destruction since there are like 'over blown' baloons in comparison to normal RBCs.And so more osmotically fragile with a certain dilute solution in comparison to other RBCs which are more resilient.


Peekay you got it in reverse.
Spherocytes are in fact more fragile. It takes less of osmotic gradient to lyse the cell. This is due to spectrin function as membrane stabilizer. it spans inner surface of the cell and supports/ressists addaptive swelling/contraction of cell in response to changes in osmolality.
Also... Hered. Spher. can be presented in mutation of Ankorin, which ataches spectrin to membrane. there are several types, depending on the specifec ankorin affected.
so... back to first question...

Spherical cells lyse at a higher concentration of sodium chloride than do normal biconcave red cells. 0.65% is higher than 0.5%... so everything should be in order.
In other words spherocyets have decreased ability to withstand hypo-osmotic evironment.
Hope this helps.


mdwannabe, Thanks.However your last paragraph is perplexing.If the NaCl is .65% then its more concentrated than spherocytosis won't the cells lyse in a more dilute/hypotonic solution???I think there must be something wrong with crista's figures about the NaCl.


If you have a keen eye,you will notice that there is no central pallor since the RBC is a sphere rather then a biconcave disk./ also there is increase unconjugated bilirubin


I'm sorry mjl717....i don't see any statement about unconjugated bilirubin or no central pallor being made in this thread??What is it in reference to?


Malaysian, spherocytes lyse at a higher conc than normal cells.
try to link concentration of NaCl with the amount of water that will go into the erithrocyte to balance the osmotic pressure.
high conc :arrow: less water into the cell,(NaCl tends to retain more water)
low conc :arrow: more water into the cell (NaCl doesnt retain water at the same level, so it goes into the cells) :arrow:

thus, as u lower the conc of NaCl , u make the spherocyte "indure" more water, u make it bigger, and u stress the membrane more. because of the fragility, their membrane will brake easier than normal ones, so they will lyse at a higher conc than normal cells. (0.65% instead of 0.50%)

i hope i helped u a little bit.........i put it as clear as i could. smiling face

all the best


Thanx Alina......I got it now.Thankx Crista for asking this question.


good dicussion :-)

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