Trapping of Sodium, Potassium, Sucrose, and Albumin in the Packed Cell Column of the Hematocrit

The observation of Maizels and Remington (1959) that high molecular markers are trapped to a significantly lower degree between centrifuged red cells (RBC) than small sized molecules, has prompted a study of the trapping of 131I-labelled albumin, sucrose-14C, 22Na and 42K. Albumin was found to be trapped to a significantly lower degree than sodium. The difference between trapping of 22Na and of 131I-labelled albumin at 0d C averaged 1.8 per cent, independent of the force and duration of centrifugation. Removal of membrane neuraminic acid had only a slight effect on trapping of albumin. The percentual trapping of 22Na and of 42K was found to equal trapping of sucrose-14C, when the rate of Na and K uptake into RBC at 0d C was considered. These rates of sodium and potassium influx at normal extracellular concentrations were 0.24 and 0.027 meq kg RBC-1 h-1. Based on the experimental findings the existence of a truly intracellular, rapidly exchangeable fraction of RBC sodium is rejected.