Scientists found that for the creatine transporter to move creatine into frog cells, it needs at least two sodium ions and one chloride ion for each creatine molecule, based on how the uptake rate changed with different sodium and chloride concentrations.
Scientific Claim
The human CRT-1 creatine transporter in Xenopus oocytes requires at least two sodium ions and one chloride ion to transport one creatine molecule, as indicated by the hyperbolic and sigmoidal concentration dependence of external Na+ and Cl- on uptake rate.
Source Excerpt
“The rate of uptake increased hyperbolically with the increasing concentration of the external Cl- (equilibrium constant KCl- approximately 5 mM) and sigmoidally with the increasing concentration of the external Na+ (equilibrium constant KNa+ approximately 56 mM). Further analyses of the Na+ and Cl- concentration dependence data suggested that at least two Na+ and one Cl- were required to transport one creatine molecule via the creatine transporter.”
Evidence from Studies
Supporting Studies
Molecular characterization of the human CRT-1 creatine transporter expressed in Xenopus oocytes.
The study directly measured the concentration dependence of Na+ and Cl- on creatine uptake in Xenopus oocytes expressing the human CRT-1 transporter. The kinetic analysis of these data led to the conclusion about the stoichiometry of ion requirements for creatine transport.