Accumulation of 131I hippurate in rat heart allografts during rejection

The accumulation of 131I hippurate in heterotopic (abdominal) rat heart allografts (Brown-Norway to Lewis) in comparison with native (autologous) hearts 6 and 7 days after transplantation was studied by noninvasive scintigraphic imaging and by direct isotope counting of excised hearts. Six hours after intravenous isotope injection, isotope accumulation in the allografted heart was clearly identified by scintigraphic study in comparison with the background, kidneys, urinary bladder, and native heart. Six and 7 days after transplantation, excised allografted hearts were significantly increased in weight in comparison with native hearts. A significant increase in isotope accumulation in allografted hearts in comparison with native hearts was found both per heart and per gram of heart. The findings of this study suggests the potential usefulness of 131I hippurate in the immunoinflammatory monitoring of organ allograft rejection by direct counting as well as by noninvasive scintigraphic study if sufficient time is allowed to permit clearance of high concentrations of isotope from the background areas, kidneys, and urinary bladder.