An improved procedure for measuring the uptake of tracer P32 by tissues in culture is described. It consisted of counting the ß-emissions through a specially designed roller tube in which the culture medium could be effectively removed from the system without opening or damaging the cultures.
In standard growth-promoting medium, the uptake was shown to be markedly greater than in Tyrode's solution. The uptake curve was found to be essentially parallel with the uptake of P32 in desoxyribo- and ribonucleic acids when standard medium was used, and in desoxyrihonucleic acid when Tyrode's solution was used. This is interpreted to signify that the total uptake of tracer phosphorus approximates the growth in the culture.
The value of uptake measurements as a frame of reference for comparison of various types of media and of metabolic studies is indicated.
