Factors which affect cerebral uptake and retention of /sup 13/NH/sub 3/. [Testing in monkeys]
The single pass extraction of ammonia (E) by cerebral capillaries was studied in vivo in Rhesus monkeys with /sup 13/N. The value of E for /sup 13/N-ammonia was found to be less than 100%, inversely related to cerebral blood flow and to be limited by the permeability of the blood brain barrier for ammonia. A vaue of the permeability surface area product was determined to be 0.0040 x 10/sup -4/ cm/sup 3//sec/gm. The single pass extraction fraction, E, for /sup 13/N-ammonia was found to be independent of arterial blood pH (in the range of 7.2 to 7.6) and of arterial blood ammonia concentration (in the range of 80-1400 ..mu..gms/100 cc). An insulin induced hypoglycemic reduction in the cerebral metabolic rate for glucose and oxygen of 54% produced a reduction in E of about 24%. When a condition of elevated arterial blood ammonia was added to hypoglycemia, the value of E and cerebral metabolic rate for oxygen remained low while the cerebral metabolic rate for glucose increased by a factor of 2.5 indicating the presence of a detoxification shunt for ammonia. Positron tomographic images of the equilibrium cross section distribution of /sup 13/N-ammonia appeared to reflect regional differences in capillary density of the cerebral tissue.
- Research Organization:
- California Univ., Los Angeles (USA). Lab. of Nuclear Medicine and Radiation Biology
- DOE Contract Number:
- E(04-1)-GEN-12
- OSTI ID:
- 7304976
- Report Number(s):
- UCLA-12-1117; TRN: 77-009693
- Country of Publication:
- United States
- Language:
- English
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AMMONIA
LABELLED COMPOUNDS
BRAIN
RADIOISOTOPE SCANNING
NITROGEN 13
RADIONUCLIDE KINETICS
BLOOD VESSELS
CAPILLARIES
MEMBRANE TRANSPORT
MONKEYS
POSITRON CAMERAS
RADIOPHARMACEUTICALS
TESTING
TOMOGRAPHY
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
BODY
CAMERAS
CARDIOVASCULAR SYSTEM
CENTRAL NERVOUS SYSTEM
COUNTING TECHNIQUES
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
GAMMA CAMERAS
HYDRIDES
HYDROGEN COMPOUNDS
ISOTOPES
LIGHT NUCLEI
MAMMALS
MINUTES LIVING RADIOISOTOPES
NERVOUS SYSTEM
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NITROGEN ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
ORGANS
PRIMATES
RADIOACTIVE MATERIALS
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550601* - Medicine- Unsealed Radionuclides in Diagnostics