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Summary The properties of the factor in human urine which stimulates mouse bone marrow colony growth in vitro were examined. The colony stimulating activity of urine was not lost on concentration of urine, exposure to RNA‐ase, DNA‐ase, ether, 8M urea, pH in the range 2–12, or on fractionation by precipitation with ethanol or ammonium sulphate. Activity was lost on heating (90°/30′), exposure to periodate and incubation with high concentrations of Pronase. There was no difference between the behaviour of the colony stimulating factor in normal and leukaemic human urine concentrates on electrophoresis and on gel‐filtration. The colony stimulating factor in urine concentrates moved in the post‐albumin‐albumin region on electrophoresis at pH 8.6 had an apparent molecular weight of approximately 190,000 on gel‐filtration and an apparent sedimentation coefficient (S 20, w ) of approximately 3.3S (zone sedimentation on sucrose gradients). A procedure was described for the extraction and partial purification of the colony stimulating factor from large quantities of human urine. The data suggest that the colony stimulating factor may be a glycoprotein and that it could belong to a family of tissue‐specific humoral growth regulating macromolecules.
Stanley et al. (1969) studied this question.