Studies on the crystalline lens. XXVI. Kinetic study showing saturation of the sodium pump.
Active transport of sodium out of rabbit lenses was shown to be carrier mediated by observing the dependence of efflux of 22Na on intracellular concentration of nonlabeled sodium which previously was elevated by incubating lenses at 0 degree C. Velocity of sodium efflux increased asymptotically with increasing concentrations of intracellular sodium, demonstrating saturation of the carrier. The maximum velocity of the sodium pump based on Michaelis-Menten kinetics was found to be 4.6 mumol/hr/lens, and the half-saturation of the carrier, which appeared to involve a single site, occurred at 36 mM.
D000818:Animals; D001693:Biological Transport, Active; D066298:In Vitro Techniques; D007700:Kinetics; D007908:Lens, Crystalline / Q000378:metabolism*; D011817:Rabbits; D012964:Sodium / Q000378:metabolism*
D012964:Sodium