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Summary: Preparations of d,/-and meso-hexamethyl propyleneamine oxime (HM-PAO) labeled with techne tium-99m were added to rat brain homogenates diluted with phosphate buffer (l: 10). The conversion of d, / HM-PAO to hydrophilic forms took place with an initial rate constant of 0.12 min -1. Incubation of the brain ho mogenate with 2% diethyl maleate for 5 h decreased the homogenate's measured glutathione (GSH) concentration from 160 to 16 f.LM and decreased the conversion rate to 0.012 min -]. Buffered aqueous solutions of glutathione rapidly converted the HM-PAO tracers to hydrophilic forms having the same chromatographic characteristics as found in the brain homogenates. The rate constant for the conversion reaction of d,l-HM-PAO in GSH aqueous solution was 208 and 317 LlmoIlmin in two different assay systems and for meso-HM-PAO the values were 14.7 and 23.2 LlmoIlmin, respectively. Rat brain has a GSH con centration of about 2.3 mM and the conversion of the d,l-HM-PAO due to GSH alone should proceed with a Over the last decade, several brain imaging ra diopharmaceuticals with sufficiently long brain res idence times to permit routine imaging by single photon emission computed tomography (SPECT) have been developed. These have included e2 3 I]_ labeled p-iodo-N -isopropylamphetamine (IMP) (Winchell et aI., 1980) and N ,N-dimethyl-N'(2-hydroxy-5-iodo-3-methylbenzyl)-1 ,3-propanediamine (HIPDM) (Tramposch et aI., 1983), eOITl] diethyldithiocarbamate (DDC) (Wyth et aI., 1983)

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Leukocytes labeled with technetium-99m hexamethylpropyleneamine oxime (HMPAO) were used in 100 patients: 32 with suspected inflammatory bowel disease, 17 with fever of unknown origin, 21 with suspected abdominal sepsis, 20 with suspected bone sepsis, seven with bronchiectasis, and three with recent myocardial infarction. The distribution of activity in patients subsequently shown not to have inflammatory bowel disease was similar to that previously described for indium-111-labeled leukocytes. However, in this study, activity was also seen in the kidneys and bladder and occasionally the gallbladder on both early (1-3 hours) and late (24 hours) views, and in the colon in late views. Migration of Tc-99m-labeled granulocytes was seen in inflammatory disease as early as 30 minutes after injection, while normal bowel activity was not seen before 4 hours. The sensitivity of Tc99m-labeled leukocytes in the detection of inflammation was 100%, the specificity was 95%.

An investigation of the efficacy of astatine-211--tellurium colloid for the treatment of experimental malignant ascites in mice reveals that this alpha-emitting radiocolloid can be curative without causing undue toxicity to normal tissue. By comparison, negatron-emitting phosphorus-32 as colloidal chromic phosphate had no antineoplastic activity. The most compelling explanation for this striking difference is the dense ionization and short range of action associated with alpha-emission. These results have important implications for the development and use of alpha-emitters as radiocolloid therapy for the treatment of human tumors.