Choroid plexus localization of 99mTc-pertechnetate.

Autoradiograms were performed on brain slices, 3 h after 99mTc-pertechnetate injection, and 24 h after previous treatment with stannous pyrophosphate. On macroautoradiograms, the radioactivity was focused entirely upon plexus areas. Silver grains were predominantly overlying the cytosol of brush border cells; less than 10% of the total plexus radioactivity was found in vascular structures. These findings suggest that a possible metabolic phenomenon exists rather than a passive distribution.