The use of 75selenomethionine for labelling the formed and protein elements of the blood.

In the introduction the authors describe the biological role of platelets, plasma protein, fibrinogen and erthrocytes as well as the methods of tagging, separating and measuring them. The advantage of platelet labelling with 75selenomethionine is that it allows production and life-span to be determined simultaneously, however, the in vivo measurements do not give information on the site of platelet sequestration. Protein anabolism as well as katabolism can be evaluated with it, and the simultaneous determination of platelet and fibrinogen turnover may be especially useful in pathological conditions. The determination of erythrocyte life-span with 75 selenomethionine does not give so much information as the 59Fe and 51Cr methods, but when used for the examination of cell kinetics in combination with the latter methods it may afford an insight into erythropoiesis. The biological and the effective half-life periods (Teff) of 75selenomethionine are probably shorter than indicated in the literature.