“…The in uiuo incorporation rates of leucine into proteins of the spinal cord, of brain stem and of heart muscle were measured using a pulse of tritiated leucine by intraperitoneal injection after which a rather uniform labelling would be expected throughout the organism (Figure 1, Table 1) (Rees, Brogan, Entingh, Dunn, Shinkman, Damstra-Entingh, Wilson & Glassman, 1974). A relatively short incorporation period (20 min) was chosen for two reasons: (a) uptake and metabolism of the radioactive precursor in the tissue was fast (Schotman, Gispen, Jansz & De Wied, 1972;Schotman, Gipon & Gispen, 1974) and (b) incorporation was taken as measure of synthesis rather than turn-over rate of proteins.…”