Journal of Applied Physiology, Vol 39, Issue 3 496-497, Copyright © 1975 by American Physiological Society
Determination of plasma volume by 113min-labeled transferrin
M. Horowitz, G. Beer and E. Loewinger
The binding property of ionic indium (In3+) with plasma transferrin was
utilized for determination of plasma volumes (PV) of whole body and
individual organs in small animals. Plasma transferrin from a donor rat was
labeled with 15-17 muCi 113mIn/ml plasma and injected into the tested rats.
PV were determined either by extrapolation to the dilution at time zero
(for whole animals) or by calculation of the ratio, organ radiation:
radiation of a plasma unit volume (for organs). The reliability of the
method for determination of whole-body PV was ascertained by comparing the
results obtained with those obtained simultaneously by the Evans blue
dilution method. Whole body PV values obtained by the two methods were
similar, with a correlation coefficient (r) of 0.997. The short half life
of 113mIn enables it to be used with other nuclides which have similar or
different energies in the same sample; indium radiation was counted first
and after it had disappeared the activity of the other nuclide could be
measured.
