The radical-scavenging antioxidants in human serum represent a heterogeneous group of substances, some synthesised in the body and some derived exclusively from the diet. Serum proteins, for example, can scavenge free radicals if they have available tyrosine or cysteine groups. Uric acid, which is also present in the serum in substantial concentrations, is another major free radical-scavenger. Circulating albumin and uric acid together provide the major source of antioxidant activity in normal human plasma. Using a synthetic radical cation, generated in the test tube as the basis for a laboratory test, the reference interval for serum total antioxidant activity is 1.32 - 1.58 mmol/L (Trolox equivalents). The reference interval for serum nutritional antioxidants (taken as the total serum activity minus that of the serum albumin and uric acid) is 450 - 800 µmol/L (Trolox equivalents). Oxidative stress, i.e. the presence of a relative excess of pro-oxidants in the extra-cellular fluid, causes a fall in these figures. Studies on diabetic patients, asthmatics, subjects with cardiovascular problems and premature babies, have confirmed the usefulness of these measurement in certain clinical situations and we feel that there are many other patients in which a knowledge of the combined activity of all the circulating antioxidants would assist in clinical assessment and care. Deficiencies of vitamin C (reference interval 34 - 114 µmol/L) or vitamin E (reference interval 25 - 60 µmol/L) usually only have a marginal effect on these figures and hence levels of these vitamins should be assessed individually.
Abstain from taking supplements (any supplements containing vitamins A,C,or E) for 12 hours prior to sampling.
Serum should be separated for samples taken outside of the UK.
antox.pdf (Click to Download)
Postal Samples Acceptable:
1. Miller NJ, Rice-Evans CA. Spectrophotometric determination of antioxidant activity. Redox Report 1996;2:161-171.
2. O’Brien SF, Watts GF, Powrie JK, Shaw KM, Miller NJ. Relationship of serum lipids, lipoproteins, and plasma antioxidants with glomerular and tubular dysfunction in insulin-dependent diabetes mellitus. Diabetes Research and Clinical Practice 1996;32:81-90.
3. Miller NJ, Johnston JD, Collis CS, Rice-Evans CA. Serum antioxidant activity after myocardial infarction. Annals of Clinical Biochemistry 1997;34:85-90.
4. Rice-Evans CA, Miller NJ. The measurement of the antioxidant status of dietary constituents, low density lipoproteins and plasma. Prostaglandins, Leukotrienes and Essential Fatty Acids 1997;57:499-505.
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