Cerebral extraction of N-13 ammonia: its dependence on cerebral blood flow and capillary permeability, surface area product. [Dogs; monkeys]

Technical Report · Mon Jan 01 04:00:00 EST 1979

DOI:https://doi.org/10.2172/5824580· OSTI ID:5824580

Phelps, M E; Huang, S C; Kuhl, D E; Hoffman, E J; Slin, C

/sup 13/N-labeled ammonia was used to investigate: (1) the cerebral extraction and clearance of ammonia; (2) the mechanicsm by which capillaries accommodate changes in cerebral blood flow (CBF); and (3) its use for the measure of CBF. This was investigated by measuring the single pass extraction of /sup 13/NH/sub 3/ in rhesus monkeys during P/sub a/CO/sub 2/ induced changes in CBF, and with dog studies using in vitro tissue counting techniques to examine /sup 13/NH/sub 3/ extraction in gray and white matter, mixed tissue, and cerebellum during variations in CBF produced by combinations of embolization, local brain compression, and changes in P/sub a/CO/sub 2/. The single pass extraction fraction of /sup 13/NH/sub 3/ varied from about 70 to 20% over a CBF range of 12 to 140cc/min/100gms. Capillary permeability-surface area product (PS) estimates from this data and the dog experiments show PS increasing with CBF. The magnitude and rate of increase in PS with CBF was highest in gray matter > mixed tissue > white matter. Tissue extraction of /sup 13/NH/sub 3/ vs CBF relationship was best described by a unidirectional transport model in which CBF increases by both recruitment of capillaries and by increases of blood velocity in open capillaries. Glutamine synthetase, which incorporates /sup 13/NH/sub 3/ into glutamine, appears to be anatomically located in astrocytes in general and specifically in the astrocytic pericapillary end-feet that are in direct contact with gray and white matter capillaries. The net /sup 13/NH/sub 3/ extraction subsequent to an i.v. injection increases nonlinearly with CBF. Doubling or halving basal CBF produced from 40 to 50% changes in the /sup 13/N tissue concentrations with further increases in CBF associated with progressively smaller changes in /sup 13/N concentrations. /sup 13/NH/sub 3/ appears to be a good tracer for the detection of cerebral ischemia with positron tomography but exhibits a poor response at high values of CBF.

• Research Organization: California Univ., Los Angeles (USA). Lab. of Nuclear Medicine and Radiation Biology
• DOE Contract Number: EY-76-C-03-0012
• OSTI ID: 5824580
• Report Number(s): UCLA-12-1225
• Country of Publication: United States
• Language: English

Related Subjects

550601 -- Medicine-- Unsealed Radionuclides in Diagnostics
560172* -- Radiation Effects-- Nuclide Kinetics & Toxicology-- Animals-- (-1987)
62 RADIOLOGY AND NUCLEAR MEDICINE
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AMMONIA
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
BLOOD FLOW
BLOOD VESSELS
BLOOD-PLASMA CLEARANCE
BODY
BRAIN
CAPILLARIES
CARDIOVASCULAR SYSTEM
CAT SCANNING
CENTRAL NERVOUS SYSTEM
CLEARANCE
DATA
DATA FORMS
DIAGNOSTIC TECHNIQUES
DOGS
DRUGS
ECAT SCANNING
ELECTRON CAPTURE RADIOISOTOPES
EXPERIMENTAL DATA
HYDRIDES
HYDROGEN COMPOUNDS
INFORMATION
ISOLATED VALUES
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
MACACUS
MAMMALS
MEASURING METHODS
MINUTES LIVING RADIOISOTOPES
MONKEYS
NERVOUS SYSTEM
NITROGEN 13
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NITROGEN ISOTOPES
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
ORGANS
PERMEABILITY
PHOTON EMISSION SCANNING
PHOTON TRANSMISSION SCANNING
PRIMATES
RADIOACTIVE MATERIALS
RADIOISOTOPES
RADIOPHARMACEUTICALS
SURFACE AREA
SURFACE PROPERTIES
TOMOGRAPHY
VERTEBRATES