On biological half-life of potassium in man

The highly sensitive whole-body counting technique makes quantitative determinations of nanocurie amounts of gamma-emitters within the body possible. So such counters are especially suitable for the long-term measurement of tracer retention and excretion rates. In the present study, the biological half-life of body potassium in ten male volunteers was determined using 42K as tracer. The group was measured using two different types of whole-body counters. A 43-cm standard chair technique was used with counter A and a multidetector linear scanning technique with counter B. The oral tracer dose of 12-15 muCi 42K to volunteers made it possible to estimate the biological half-life of potassium, which varied from 10 to 28 days, the mean being 16 days. The total body potassium determinations were carried out with the 42K- and 40K-methods. The results of the parallel determinations performed with Counter A agreed well with those of Counter B. A good consistency was also found in the body potassium values of individual subjects, obtained using both the methods separately for each counter.