EFFECT OF TRIPHENYL TETRAZOLIUM CHLORIDE STAINING ON THE DISTRIBUTIONOF RADIOLABELED PHARMACEUTICALS

Myocardial tissue is routinely exposed to the vital stain triphenyl te trazolium chloride (TTC) to.delineate infarction in conjunction with m yocardial isotope research. However, it is unknown whether TTC has a d irect effect on tracer deposition. We evaluated this possibility in ra bbit hearts injected with either teboroxime, sestamibi or Tl-201. The hearts were excised and treated as follows: (1) TTC or normal saline w as perfused through the heart and the residual activity monitored; (2) hearts were sliced into 0.5-cm thick sections, counted and incubated in either TTC or normal saline for 10 min then recounted; and (3) the circumflex artery was ligated postmortem and TTC perfused. Autoradiogr aphic images were produced from 30-mum slices to depict any disparity in activity concentration from the selective perfusion of TTC. Both pe rfusion and incubation by TTC resulted in a significant activity loss of both Tl-201 and sestamibi, but not teboroxime, compared to normal s aline. An independent octanol extraction experiment measured the chang e in the partition coefficient of labeled teboroxime and sestamibi ind uced by the addition of TTC. TTC was shown to liberate the radiolabel from sestamibi, but not from teboroxime. We conclude that histochemica l staining techniques involving TTC can after the distribution of radi o-labeled pharmaceuticals. As a result, experiments using TTC with Tl- 201 and sestamibi should be interpreted cautiously.