Gallium transferrin

Ga-citrate is also commonly used for imaging infection and inflammation. " At sites of inflammation, the gallium-transferrin complex leaks into the extracellular space and Ga is transchelated from transferrin in blood to lactoferrin and siderophores see Iron Transport Siderophores), which are released by leukocytes and bacteria. Imaging with Ga takes place usually 24-72h following injection. 

When galllum-67 is injected into the bloodstream as either chloride or citrate, it rapidly becomes bound to serum proteins, especially transferrin (5 53 54). Although the gallium-transferrin interaction is weaker than that of iron and... 

Farrar G, Altmann P, Welch S, Wychrij O, Ghose B, Lejeune J, Corbett J, Prasher J Blair JA. (1990). Defective gallium-transferrin binding in Alzheimer disease and Down syndrome Possible mechanism for accumulation of aluminum in brain. Lancet 335, 747-750. 

Gallium is non-essential, but on account of the similarity between Ga3+ and Fe3+ it binds to iron transport and storage proteins such as transferrin and ferritin. The radioactive isotope of gallium, 67Ga, concentrates to a large extent in many tumours and at sites of inflammation and infection, and since many tumours overexpress the transferrin receptor it can be used for tumour imaging. 

Serum transferrin is normally only about 30% saturated with iron. This explains why it has a relatively high capacity for binding other metals and so is implicated in the transport of 67Ga,1139 which is used as an imaging agent for various soft tissue tumours and inflammatory abscesses.1140 Transferrin also facilitates movement of gallium across tumour cell membranes.1141... 

Radunovic A, Delves HT, Bradbury MWB. 1998. Uptake of aluminum and gallium into tissues of the rat. Influence of antibody against the transferrin receptor. Biol Trace Elem Res 62 51-64. 

Gallium can interfere with the structural integrity of transferrin, the ircin-binding protein that transports iron in the serum. Gallium is believed to bind in the protein methionine. In microorganisms like Escherichia coli, gallium suppresses the synthesis of low-molecular weight polypeptides. It also concentrates on the surface of the cell envelope. 

E27.5 Gallium(III) can bind to transferrin and lactoferrin, and can even be incorporated into ferritin (a biological iron storage ). These enzymes use nitrogen and oxygen donors to bind iron. Since Ga(III) also has a good affinity for the same donors, it can compete with Fe(III) for the binding sites. One major difference between Fe(lll) and Ga(lII) is their redox chemistry. While Fe(Ill) can be reduced to Fe(II), Ga(Ill) cannot. This is an important... 

Larson SM, RaseyJS, Allen DR andGRUNBAUMZ (1979) A transferrin-mediated uptake of gallium-67 by EMT-6 sarcoma. II. Studies in vivo (BALB/c Mice) Concise communication. J Nucl Med 20 843 -846. 

Sephton RG and Harris AW (1975) Gallium-67 citrate uptake by cultured tumor cells, stimulated by serum transferrin. J Natl Cancer Inst 54 1263 — 1266. 

Lactoferrin, with a molecular weight of 8.5-9.0 x 10 and a structure similar to transferrin (112) has been suggested as an alternative intracellular gallium-binding agent (113). 

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