Effects of N-Methyl-N-nitrosourethane on Cells in Tissue Culture

Abstract

A COMMUNICATION on the morphological conversion of cells in vitro by N-nitrosomethylurea by Sanders and Burford¹ prompts me to report similar experiments performed about 5 years ago in which the related and very effective carcinogen, N-methyl-N-nitrosourethane (MNU)² was used. Its action in vitro was tested on various mammalian cells grown in tissue culture. These included the Syrian hamster fibroblast BHK 21/13 C cell line³ made available by Professor M. Stoker, and also fresh cultures of trypsinized baby (or foetal) rat heart fibroblasts. The cultures were maintained in Roux bottles, in Eagle's medium (containing double concentration of amino-acids and vitamins) and Hanks tryptose phosphate broth with 10 per cent calf serum. The cultures were trypsinized and sub-cultured once a week or more often. Explants, 24 h or 48 h old, were used for treatment with MNU of concentrations 1 × 10⁻² – 1 × 10⁻⁵ molar. For this purpose, the medium was removed from the cultures and replaced by MNU dissolved in ethanol (1 : 10 v/v) and diluted to the desired concentration with phosphate buffer. After 30 or 60 min at 37° C, the MNU solution was decanted, the cultures were washed once with phosphate buffer, and left in fresh medium at 37° C.