| Range |
~14,000 fold
|
| Organism |
Human Homo sapiens |
| Reference |
Forster RE, Gros G, Lin L, Ono Y, Wunder M. The effect of 4,4'-diisothiocyanato-stilbene-2,2'-disulfonate on CO2 permeability of the red blood cell membrane. Proc Natl Acad Sci U S A. 1998 Dec 22 95(26):15815-20. p.15816 left column bottom paragraph & p.15819 left column 2nd paragraphPubMed ID9861053
|
| Method |
"The reactions take place in an
airtight 3-ml glass water-jacketed and stirred chamber connected
to the ion source of a mass spectrometer through a thin
0.012-mm-thick Teflon membrane supported by a sintered
glass disc, through which gases are dissolved in the solution
diffuse. The chamber has a glass pH electrode and a removable
stopper for the addition of reactants." |
| Comments |
"The initial rapid phase is
produced by 12C18O16O diffusing into the cells, where the 18O
is exchanged with HOH at a rate accelerated some 14,000
times by intracellular CA [carbonic anhydrase]. This rapid intracellular consumption
of 12C18O16O in relation to its production at the uncatalyzed
rate from extracellular HC18O16O3 lowers 12C18O16O in the
extracellular solution...The rate of O2 uptake by red cells is about 1/30th of that in
hemolysate, owing to the effect of simultaneous chemical
reaction and diffusion, in distinct contrast to CO2, a fact that
deserves explanation. This difference results simply because
the velocity constant k in Eq. 3 for O2 is 3,500mM^1Xsec^1X18mM hemoglobin, equal to 63,000 sec^-1, 1,400 times larger
than the exchange velocity constant for 18O in CO2, making
average cell [O2] about 1/30 of the surface concentration
according to Eq. 3." |
| Entered by |
Uri M |
| ID |
110584 |