Erroneous Measurement of Plasma Volume in the Rabbit by T-1824

When measurements of plasma volume are made in rabbits with T-1824 and rabbit albumin labeled with I 131 , the dye value averages 1.09 of the labeled albumin value. This dye value is in error, and the probable cause is loss of a fraction of the dye from the circulation immediately after the dye injection. Comparison of the later rates of loss of T-1824 and I 131 -albumin from the circulation shows that the dye is lost at nearly double the rate of loss of I 131 -albumin. T-1824 is thus an unsatisfactory label for rabbit albumin, and cannot be used for measurements of rabbit plasma volume. When F cells (body hematocrit/venous hematocrit) is measured with P 32 -labeled cells and I 131 -albumin the average value in rabbits is 0.895.