Seminars in oncology vol:28 issue:2 Suppl 8 pages:24-8
Blood functions as a mobile tissue in an exchange system, with the remaining body tissue as a stationary phase. The equilibrium among plasma water, plasma proteins, and blood cells is described by models, but little consideration has been given to the substance-binding capacity of erythrocytes. There are numerous reasons for this, including bioanalytical limitations (ie, it has been difficult to study erythrocytes in the laboratory in their natural state). Erythrocyte monitoring requires accurate blood sampling and quantitative isolation of erythrocytes without disturbing the equilibrium of substances of interest between erythrocytes and plasma or other blood constituents. This became possible with the advent of the measurement of sediment device. The mass of a given substance available in blood can be described by M(Blood) = M(Plasma) + M(ERY) (+ M(REM)). M(ERY) is the mass of a substance present in erythrocytes and it is shown that for several oxazaphosphorines, such as iphosphoramide mustard, that M(ERY) determines M(Blood) with great superiority over M(Plasma). The impact of erythrocyte monitoring on therapeutic outcome has to be defined, but is an important area of research.