Our last work on IODINE:
for request of comments
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Presented at ì SELENIUM 2000î :
7th International Symposium on Selenium in Biology and Medicine. October
1-5, 2000
Venezia (Italy); Abstract P-88 :134
ì SELENIUM AND IODIDE: ANCIENT ANTIOXIDANTS OF CELLULAR MEMBRANE
LIPIDS ? ì
Massimo Cocchi and * Sebastiano
Venturi.
Scottish Agricultural College, Edinburgh and *Servizio díIgiene USL
n.1- Novafeltria (PS), Italy
E-mail:
venturis@nf.infotel.it
Over three billion years ago, blue-green algae (Cyanobacteria) ancestors
of eukaryotic algae which contain high amount of iodine and selenium,
were the first living cells to produce oxygen in the terrestrial
atmosphere. So, algal membrane lipids and polyunsaturated fatty acids
(PUFAs) required a protective antioxidant action in which iodide and
selenium might have had this specific role. In fact, iodides and
selenium are greatly available in seawater, where algal phytoplankton,
the basis of marine food-chain, which is rich in PUFAs, acts as a
biological accumulator of both of these trace elements (1). PUFAs and in
particular Arachidonic Acid (AA, omega-6) and Docosahexaenoic Acid (DHA,
omega-3) are essential for animal development and for cell membrane
structure and function. DHA itself stimulates in cells the activites of
catalase, glutatione-peroxidase and GSH.
Recently, we have hypothesised that iodide might have an ancestral
antioxidant function in all iodide-concentrating cells from primitive
algae to more recent vertebrates (2-3). There is an interesting chemical
gradient of electronegativity, according to Pauling-scale units, among
Oxygen (3.44), Iodide (2.66), Selenium (2.55), which may explain their
role in electron transfer into oxygen of H2O2 via peroxidase enzymes. In
the cells iodide acts as an electron donor in the presence of H2O2 and
peroxidase, and the remaining iodine atom readily iodinates the tyrosine
or the histidine or some specific PUFA, and so, it neutralizes its
oxidant power. Iodine can add to double bonds of PUFAs, making them
less reactive to free oxygen radicals. These iodolidips (iodo-lactone,
iodo-AA, iodo-DHA) have structural and probably metabolic functions in
vegetable and animal cells.
In our current research we are studying iodide, selenium and PUFAs in
different conditions during chick embryo development (4).
REFERENCES
1. Cann SA et al. 2000. Hypothesis: iodine, selenium and the development
of breast cancer. Cancer
Causes Control; 11(2):121-7
2. Venturi S et al. 2000. Role of iodine in evolution and carcinogenesis
of thyroid,
breast and stomach. Advances in Clinical Pathology; 4, 1:11-17
3. Venturi S et al. 2000 Environmental Iodine Deficiency: A Challenge
to the Evolution of
Terrestrial Life? Thyroid; 10, 8 727-9
4. Cocchi M and Venturi S. 2000. Iodide, antioxidant function and
omega-6 and omega-3 fatty acids.
Progress in Nutrition; 2, 1:15-19
.
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