[Variability of some isotopic characteristics of carbon in man]

Variability of some carbon isotope characteristics in man (i.e. carbon isotope composition of hair, blood, nails, expiratory carbon dioxide) was studied. Slow (with the period about 20-30 days) oscillations near some average level with a variable amplitude were observed in the isotope composition of the hair carbon. The maximum deviation from the mean level in one person tested was 6%. In the isotope composition of carbon dioxide respired under physical load and under conditions of aerobic metabolism during short periods (up to 15 minutes) there were also found significant variations from the mean level, the maximal ones being 6/1000. An attempt was made to explain the changes observed of isotope characteristics in terms of the principal carbon isotope fractionation cell model proposed earlier.