In vitro interaction between 99Tcm-labeled pyrophosphate, 32P-labeled pyrophosphate and rat tissues.

Whole-body sections from young rats were incubated with solutions containing 32P-labeled pyrophosphate, 99Tcm-labeled pyrophosphate and 99Tcm-pertechnetate, respectively, at pH 7.6 or pH 8.6. After incubation, the sections were used for autoradiography and/or staining in order to visualize tissue affinity for 99 Tcm and areas of pyrophosphatase activity. At pH 7.6, the distribution patterns of 99Tcm-labeled pyrophosphate and 32P-labeled pyrophosphate were similar. When pH was raised to 8.6, 99Tcm-labeled pyrophosphate was degraded before reaching the tissues and their enzymes. The distribution pattern of 99Tcm-labeled pyrophosphate at pH 8.6 was similar to that of 99Tcm-pertechnetate. 32P-labeled pyrophosphate could serve as a substrate for alkaline pyrophosphatase and the enzyme activity was demonstrated autoradiographically.