Red blood cell choline. II: Kinetics in Alzheimer's disease

The kinetic parameters of choline uptake into red blood cells from patients with Alzheimer's disease and normal elderly controls were compared. The Kd and Vmax values for choline uptake into red cells were determined based on a kinetic analysis of choline uptake at six different concentrations of labeled extracellular choline. The theoretical choline uptake, representing the initial rate of choline influx into choline-depleted red cells given the plasma choline concentration and the kinetic parameters of choline uptake, was also calculated. Alzheimer's disease patients and normal controls did not differ in any kinetic parameter of choline uptake. Kd and Vmax values for red cell choline uptake were strongly correlated among normal controls, but not among patients with Alzheimer's disease. In addition, among the patients with Alzheimer's disease, the theoretical choline uptake was strongly correlated with the severity of dementia. The possible significance of these findings in relation to altered choline metabolism in Alzheimer's disease is discussed.