The effect of membrane filters on cultured cells

The use of membrane filters for filtration of serum-containing culture media can change a medium in such a way that cells cultured therein attain a significantly higher lactate-glucose metabolism than the same type of cells cultured in unfiltered medium. Five different filertypes were examined, but the response was only found after filtration with MF-filters of Millipore (mixed esters of cellulose). Furthermore, in two of the three cell lines examined minor growth inhibitions were also observed. The MF-filters were found to contain a compound bound to the filter material so that serum-containing medium, but not serum-free medium, or water, could extract it in amounts sufficient for metabolic - and growth effects. The compound in MF-filters is closely related to Triton-X-100 both with respect to u.v.-spectra and to biological effects.