|
Karl-Dimiter Bissig |
Whole Animal Copper Flux Assessed by Positron Emission Tomography in the Long-Evans Cinnamon Rat − a Feasibility Study. |
|||||||||||||||
|
Michael Honer |
Supplementary material to Bissig et al. (2005) BioMetals 18, 83-88. Medline Citation. |
|||||||||||||||
|
Karl H. Summer |
|
|||||||||||||||
|
Summary |
Copper is an essential trace element. However, excess copper can lead to oxidation of biomolecules and cell damage and copper levels must be carefully controlled. While copper homeostasis has been studied extensively at the cellular level, short-term body copper fluxes are poorly understood. Here, we assessed the feasibility of measuring whole body copper flux by positron emission tomography, using 64Cu. The Long-Evans cinnamon (LEC) rat was compared to a wild type control. LEC rats are an accepted model for Wilson disease, an inherited disorder of copper excretion in humans. In LEC rats as well as in Wilson patients, the copper transporting ATPase, ATP7B, is defective. This ATPase is primarily expressed in the liver and serves in copper secretion via the bile. Dysfunction of ATP7B leads to accumulation of copper in the liver. Rats were transgastrically injected with 10 µg of 64Cu and the copper flux followed for three hours by whole animal PET. I was found that the administred copper was largely trapped in the stomach and the proximal intestine, and without a significant difference between control and LEC rat. The trapping of orally administered copper in the gastrointestinal tract may be an important mechanism to prevent copper toxicity under conditions of a sudden, excessive copper load, which cannot be alleviated by increased biliary secretion. This trapping does however limit the utility of PET to measure whole animal copper flux. |
|||||||||||||||
|
Animal Methods |
Animal experiments were performed under pentobarbital anesthesia (50 mg/kg, intraperitoneally). Right after animals had been anaesthetized, an abdominal incision was made in order to access the abdominal cavity. Bile flow was measured by cannulation of the bile duct with a polyethylene tube and external drainage and fractionation with a fraction collector. 10 µg Cu2+ (applied as a CuSO4 solution) with a specific γ-activity of 17.3 MBq/µg copper (15.13 MBq of 64Cu and 2.19 MBq of 67Cu) was introduced into the stomach by transgastric injection. Immediately after injection, the abdominal incision was adapted and the PET analysis was started. |
|||||||||||||||
|
PET Aanalysis |
PET experiments were performed with the 16-module variant of the quad-HIDAC tomograph (Oxford Positron Systems, Weston-on-the-Green, UK). The camera had four detector banks each comprising four HIDAC (high density avalanche chamber) modules. Each module consists of a multi-wire proportional chamber between lead layers containing a matrix of holes of 0.4 mm in diameter and 0.5 mm pitch. The field of view is 280 mm axially and 170 mm in diameter allowing the acquisition of whole body images in a single bed position. Anesthetized animals were fixed with adhesive tape and positioned in the camera such that the whole body was placed symmetrically in the center of the field of view. Body temperature was controlled by a rectal probe and kept at 37.3°C by a thermocoupler and a heated air stream. Acquisition of PET data was initiated right after application of the radiotracer and lasted for 3 hours. PET data were acquired in list-mode and reconstructed using the OPL-EM algorithm (Reader et al., 1998) with a bin size of 0.5 mm, a matrix size of 200x200x500, and resolution recovery with width 1.3 mm. Reconstruction did not include scatter, random, attenuation and decay correction. 7 time frames were reconstructed: 0-15 min, 15-30 min, 30-45 min, 45-60 min, 60-90 min, 90-120 min, 120-180 min. The volumetric image files of the first and last time frame were represented in 3D using the software VGStudio Max 1.1 (Volume Graphics GmbH, Heidelberg, Germany). |
|||||||||||||||
|
Data |
|
Back to the Homepage of the Swiss Copper Group
Last updated: May 17,
2005.