Nav: Home

Zn-InsP6 complex can enhance excretion of radioactive strontium from the body

June 01, 2018

[Background]

90Sr (t1/2 = 29.1 y) is one of the most important nuclear fission elements. After the nuclear power plant disasters of Chernobyl and Fukushima Daiichi, 90Sr was released into the atmosphere and the ocean. 90Sr is harmful to humans because 90Sr has a long half-life, and its daughter radionuclide, 90Y (t1/2 = 64.1 h), emits high-energy beta particles. It has been reported that internal exposure to 90Sr could be associated with the development of leukemia and osteosarcoma. Therefore, compounds inhibiting the absorption of radiostrontium from the gastrointestinal tract into the bloodstream and enhancing its elimination after intake can decrease the absorbed radiation dose of people exposed to radiostrontium. Indeed, basic research has shown that alginate can promote the excretion of 90Sr.

Myo-inositol-hexakisphosphate (phytic acid: InsP6, Figure 1) is a natural compound that abounds in plants, especially in whole grains, cereals, legumes, seeds, and nuts. Due to its structure, InsP6 exhibits high chelation potential with many kinds of metal cations. Recently, we prepared complexes of InsP6 with zinc or lanthanum ions (Zn-InsP6 and La-InsP6, respectively) and evaluated them as radiocesium decorporation agents, because both complexes are insoluble in water and are spacious enough to potentially accommodate additional metal cations coordinated by chelation. In fact, InsP6 is soluble in water, but chelation with zinc or lanthanum ions decreases the solubility in water, and thereby reduces the absorption in the intestinal tract.

In this study, we hypothesized that Zn-InsP6 and La-InsP6 can work as 90Sr decorporation agents and evaluated their potential in vitro and in vivo. Experiments using normal mice were performed to evaluate the influence of Zn-InsP6 on the biodistribution of radiostrontium. In these experiments, we replaced 90Sr with 85Sr (T1/2 = 64.8 d) because 85Sr emits gamma rays, which are easy to measure.

[Results]

Adsorption capacity of Zn-InsP6 and La-InsP6 for strontium was evaluated by the Langmuir model. The amount of strontium bound to Zn-InsP6 and La-InsP6 increased linearly at low strontium concentrations, and plateaued at high strontium concentrations, indicating saturation of the adsorption sites (Figure 2). These data meet the requirements of the Langmuir adsorption model, indicating the correctness of the assumption that the adsorbate acts as a uniform surface with finite identical binding sites characterized by monolayer adsorption of the adsorbate. The maximum sorption capacity of Zn-InsP6 and La-InsP6 was estimated as 133.7 and 6.4 mg Sr/g, respectively.

To evaluate whether Zn-InsP6 can enhance the elimination of 85Sr from the body in vivo, 85SrCl2 was orally administrated to mice just after oral administration of Zn-InsP6 suspension. As the results, pretreatment with Zn-InsP6 significantly decreased the accumulation of radioactivity in the bone and the blood after oral administration of 85SrCl2. These results indicate that Zn-InsP6 inhibited the absorption of 85Sr2+ from the intestine into the bloodstream and enhanced the excretion of 85Sr2+ in the feces.

[Significance and future prospects]

Extrapolating from the results of the biodistribution experiments, the estimated effective dose of 90Sr radiation in a human treated with Zn-InsP6 is approximately half of that of the control group. Therefore, Zn-InsP6 presents as a promising 90Sr decorporation agent.

We suppose that the Zn-InsP6 complex could improve the biodistribution of some radiopharmaceuticals and decrease the unnecessary radiation dose of patients, and it is currently under investigation.
-end-


Kanazawa University

Related Zinc Articles:

A nanoscale laser made of gold and zinc oxide
Tiny particles composed of metals and semiconductors could serve as light sources in components of future optical computers, as they are able to precisely localize and extremely amplify incident laser light.
Zinc lozenges did not shorten the duration of colds
Administration of zinc acetate lozenges to common cold patients did not shorten colds in a randomized trial published in BMJ Open.
Dietary zinc protects against Streptococcus pneumoniae infection
Researchers have uncovered a crucial link between dietary zinc intake and protection against Streptococcus pneumoniae, the primary bacterial cause of pneumonia.
Zinc could help as non-antibiotic treatment for UTIs
New details about the role of zinc in our immune system could help the development of new non-antibiotic treatment strategies for bacterial diseases, such as urinary tract infections (UTIs).
Zinc deficiency may play a role in high blood pressure
Lower-than-normal zinc levels may contribute to high blood pressure (hypertension) by altering the way the kidneys handle sodium.
Genetic polymorphisms and zinc status
Zinc is an essential component for all living organisms, representing the second most abundant trace element, after iron.
Autism is associated with zinc deficiency in early development -- now a study links the two
Autism has been associated with zinc deficiency in infancy. While it is not yet known whether zinc deficiency in early development causes autism, scientists have now found a mechanistic link.
Can chocolate, tea, coffee and zinc help make you more healthy?
Ageing and a low life expectancy are caused, at least partly, by oxidative stress.
Zinc oxide nanoparticles: Therapeutic benefits and toxicological hazards
Despite the widespread application of zinc oxide nanoparticles in biomedicine, their use is still a controversial issue.
Preconception zinc deficiency could spell bad news for fertility
The availability of micronutrients in the ovarian environment and their influence on the development, viability and quality of egg cells is the focus of a growing area of research.
More Zinc News and Zinc Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.