A cytotoxicity assay using 3H-uridine and emulsions scintillator

In immunological studies, cytotoxicity assay are extremely important. The assay method was modified so that the radioactivity of beta-decaying isotopes in a large volume of aqueous sample could be counted. Through tests of various scintillators, it was found that emulsion scintillators had a higher counting efficiency than toluene- or dioxane-based scintillators. The results obtained by this method using an emulsion scintillator agreed well with those obtained by the 51Cr release method. The advantages of the emulsion scintillator method are as follows: (a) the activity of a beta-decaying isotope can be counted in a large volume of aqueous sample, (b) a long half-life beta-decaying isotope can be used, (c) the effects of free labeled materials can be eliminated by simple procedures, and (d) no gamma counter is needed.