250-300 molecules/per µm^2 of membrane
||Guinea Pig Cavia porcellus
||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
||Animals killed, caecum dissected, put in Krebs solution and rinsed with tritiated (radioactive) oubain solutions of differing concentrations
||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."