Inhibitors of Cell Growth: Accumulation and Concentration
Animal cells cultivated in conditioned medium stop growing, even if a sufficient nutrient supply is guaranteed. Autocrine cell growth inhibitors secreted into the culture medium are responsible for this effect.
The objective of this investigation was the determination of components of conditioned medium which cause low growth rates and cell death. We found that other secreted inhibitors must exist than the metabolites ammonia and lactate.
In order to provide considerable amounts of inhibitory cell culture supernatant for characterisation and purification of the growth inhibitors, a special fermenter system was used. The supernatant produced in this system was concentrated and fractionated. The fractions were tested in a bioassay for inhibition. A dose-dependant effect was observed. Very low concentrations and high efficacy were determined. Several methods were used to obtain a high concentration of these substances. The experiments showed a molecular weight of the inhibitor(s) of less than 5000 Da.
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