Release of vitamin B12 from carrier erythrocytes in vitro

Abstract

Resealed erythrocyte ghosts (carrier erythrocytes) are potential in vivo carriers for exogenous enzymes or drugs, but data on carrier erythrocyte survival and clearance rate in humans are not available. We have measured the in vitro efflux of vitamin B₁₂ encapsulated in human red cell by hypo-osmotic dialysis, as a preliminary for its use as a marker for in vivo human studies. Vitamin B₁₂ was encapsulated into erythrocytes at a relative incorporation efficiency of 60%. In vitro hemolysis of carrier erythrocytes was minimal over 40 h, but vitamin B₁₂ was rapidly lost from the cells, effluxt/2 was 5 h, presumably by diffusion through the intact cell membrane. Vitamin B₁₂ (Vit B₁₂) may, nevertheless, be a suitable marker for short-term human studies on carrier erythrocyte splanchnic clearance.