Radioactive iodine exchange reaction of HIPDM: Kinetics and mechanism

Conference · Wed May 01 04:00:00 EDT 1985 · J. Nucl. Med.; (United States)

OSTI ID:6758151

Liu, B L; Chang, J; Sun, J S; Billings, J; Blau, M; Kung, H F

HIPDM is a lipid-soluble diamine which crosses the blood brain barrier and displays a long brain retention time. In conjunction with single photon emission computed tomography (SPECT), I-123 HIPDM has been applied clinically for studying regional cerebral perfusion. Labeling of HIPDM with radioactive iodine is simple and amenable to a kit form. In spite of the simplicity of the exchange reaction, occasionally the reaction may show low labeling yield with no apparent explanation for the failure, especially when pure (p,5n) I-123 sodium iodide was used. The authors have found that in the presence of a small amount of reducing agent, sodium bisulfite (20 ..mu..g/ml), lowered the labeling yield (from 98% to 1%), while an oxidizing agent iodate (50 ..mu..g/ml) enhanced the yield and reaction rate. The mechanism of this exchange reaction probably involves the initial formation of an electrophilic intermediate, I/sup +/. Trace metal ions (Fe/sup +3/, Al/sup +3/, Zn/sup +2/, Mg/sup +2/, Ni/sup +2/) showed negligible effects, but Cu/sup +2/ ion lowered the labeling yield (from 98% to 92%). In order to study this reaction further, they have investigated systematically the kinetics and mechanism. The exchange reaction is temperature dependent, and the graph of ln(1-F) vs. time at various temperatures (40/sup 0/ to 100/sup 0/C) showed linear relationship, indicative of a simple isotope exchange reaction (optimal reaction condition: pH 2-3, heating at 100/sup 0/C for 30 min.). By using a sodium iodide carrier-added reaction and measuring the reaction rate at three different temperatures, the activation energy for this exchange reaction is determined: Ea = 30.6 Kcal/mole. This information may be helpful in understanding the exchange reaction of HIPDM and other molecules labeled by the same type of iodine exchange reaction.

• Research Organization: Dept. of Chemistry, Beijing Normal Univ., Beijing
• OSTI ID: 6758151
• Report Number(s): CONF-850611-
• Conference Information: Journal Name: J. Nucl. Med.; (United States) Journal Volume: 26:5
• Country of Publication: United States
• Language: English

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38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
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62 RADIOLOGY AND NUCLEAR MEDICINE
ACID SULFITES
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
AMINES
BETA DECAY RADIOISOTOPES
BODY
BRAIN
CARRIERS
CENTRAL NERVOUS SYSTEM
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
CHEMISTRY
COMPUTERIZED TOMOGRAPHY
COPPER COMPOUNDS
DIAGNOSTIC TECHNIQUES
ELECTRON CAPTURE RADIOISOTOPES
EMISSION COMPUTED TOMOGRAPHY
ETHERS
HALIDES
HALOGEN COMPOUNDS
HALOGENATION
HETEROCYCLIC COMPOUNDS
HOURS LIVING RADIOISOTOPES
INORGANIC PHOSPHORS
INTERMEDIATE MASS NUCLEI
IODIDES
IODINATION
IODINE 123
IODINE COMPOUNDS
IODINE ISOTOPES
IRON COMPOUNDS
ISOTOPES
KINETICS
LABELLING
LIPIDS
MAGNESIUM COMPOUNDS
MEDIUM TEMPERATURE
MORPHOLINES
NERVOUS SYSTEM
NICKEL COMPOUNDS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
ORGANS
OXIDIZERS
OXYGEN COMPOUNDS
PH VALUE
PHOSPHORS
RADIOCHEMISTRY
RADIOISOTOPES
REACTION KINETICS
REDUCING AGENTS
SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY
SODIUM COMPOUNDS
SODIUM IODIDES
SOLUBILITY
SULFITES
SULFUR COMPOUNDS
TIME DEPENDENCE
TOMOGRAPHY
TRACE AMOUNTS
TRANSITION ELEMENT COMPOUNDS
YIELDS
ZINC COMPOUNDS