Survival of sucrose-loaded erythrocytes in the circulation

Abstract

IN an attempt to clarify the mechanism of cell lysis under intense electric fields^1–5, we have found that aqueous pores are introduced into human erthrocyte membranes when an isotonic suspension of red cells is exposed to an electric field of a few kV cm⁻¹ for a duration in μS range. These pores are formed when the transmembrane potential induced by the externally applied field exceeds a critical value of 1 V. The effective radius of the pores is several Å, and can be varied by the adjustment of field intensity, field duration, and the ionic strength of the medium. The pores remain open at low temperatures but close completely on incubation at 37 °C. In a proper medium, the resealing of perforated cells takes place without haemolysis, allowing us to prepare erythrocytes (not ghosts) of altered intracellular composition. In particular, foreign molecules such as sucrose have successfully been incorporated into resealed erythrocytes, which were apparently intact at least in terms of cell volume, cell shape, glucose transport, and Na–K pump activity⁴. Thus we have suggested that erythrocytes loaded with a drug by this technique might serve as intravenous drug reservoirs which slowly release the drug molecules into the circulation. Here we demonstrate that erythrocytes loaded with sucrose survive in the circulation with a lifetime almost indistinguishable from that of normal cells, and that the sucrose remains entrapped within the cells. For drugs that slowly permeate the erythrocyte membranes, therefore, our technique offers a means of sustaining a low plasma level for a long period of time, and this could be advantageous in clinical and other situations.