A Non-radiometric Approach to Determine Tissue Vascular Blood Volume in Biodistribution Studies

The aim of this research was to develop a reliable non-radiometric method to measure the residual blood in tissue without the need for perfusion or radiometric measurements in biodistribution studies. It was found that the perfusion method not only was ineffective in removing blood from tissue, but also introduced additional variability in the determination of tissue drug exposure and was not reproducible across studies. In addition, the use of hemoglobin as an endogenous protein and biomarker for tissue blood content was studied and it was found that hemoglobin measurement in tissue was not a reliable and effective approach for determination of residual blood level in tissue. To evaluate an alternative method for addressing the tissue blood level in biodistribution studies, animals were dosed with a Residual Blood Determinant Reagent (RBDR) 5 min prior to tissue harvesting. The level of RBDR, an exogenous protein, was measured in whole blood homogenate and in tissue lysate. Based on the level of the RBDR, the vascular blood volume (VBV) in tissue was calculated and then the tissue exposures were corrected based on the blood volumes. The tissue VBVs measured by the RBDR method were comparable with the literature values obtained by radiometric measurements.

Automated summary

The aim of this research was to develop a reliable non-radiometric method to measure residual blood in tissue without the need for perfusion or radiometric measurements. The study found that perfusion method was ineffective in removing blood from tissue and introduced variability in determining tissue drug exposure. Hemoglobin measurement was also found to be an unreliable approach. An alternative method using RBDR was developed, which showed comparable results to radiometric measurements in determining tissue blood volume.