Direct Determinations of Plasma, Cell, and Organ-Blood Volumes in Normal and Hypervolemic Mice

Direct single and combined cell- and plasma-volume determinations were made on normal and polycythemic mice with 32P-tagged red cells and 131I-tagged plasma. The data indicate that: (a) The Evans-blue plasma volumes in mice are above the probably more correct 131I-plasma volumes by a factor of 1.2 and in rabbits by a factor of 1.08. (b) The so-called mixing time of Evans blue is a withdrawal time of this dye by Evans blue-affin cells, most of which are probably macrophages. (c) The cell volume calculations based on Evans-blue values are higher than those obtained by direct determinations with the 32P technic by a factor of 1.56 in normal and 1.51 in tumor-bearing mice tested. (d) The average body hematocrit in mice is approximately 0.88 times the venous hematocrit. (e) On the basis of these conversion values a calculation of all values can be made if only one technic is employed (Fig. 1). (f) Hypervolemia caused by estrogen-secreting tumors is attributable to an almost selective plasma-volume rise while that with luteoma is due primarily to polycythemia and, to a lesser extent, to a plasma volume rise.