Number of ouabain molecules bound to sodium-potassium pump when completely saturated

Range 250-300 molecules/per µm^2 of membrane
Organism Guinea Pig Cavia porcellus
Reference Brading AF, Widdicombe JH. An estimate of sodium-potassium pump activity and the number of pump sites in the smooth muscle of the guinea-pig taenia coli, using (3H)ouabain. J Physiol. 1974 Apr238(2):235-49. abstractPubMed ID4840873
Method Animals killed, caecum dissected, put in Krebs solution and rinsed with tritiated (radioactive) oubain solutions of differing concentrations
Comments Abstract: "1. Binding of tritiated ouabain to the smooth muscle of the guinea-pig taenia coli showed two components, one saturable at lower glycoside concentrations and the other linear with increasing concentrations. 2. The saturable component alone was affected by extracellular potassium concentrations. This component seems to be bound to sodium pumping sites, and when completely saturated binds 1.1×10^11 molecules per mg fresh wt. of tissue, or 250–300 molecules per square micron of membrane, assuming a volume:surface area ratio of 1.5 μm."
Entered by Uri M
ID 103030