The Effect of Corticotropin on Mouse Spleen Colony-forming Cells

Several investigators have reported a reduction in the number of colony-forming units (CFU) in the spleens of mice exposed to hypoxia and have postulated that this is secondary to a direct toxic effect of hypoxemia on the CFU. To test the hypothesis that at least part of this effect could be secondary to the stress of the hypoxic exposure, mice were given 12 consecutive daily injections of corticotropin (ACTH), and the number of spleen and marrow CFU were assayed by the spleen colony technique. There was a marked decrease in spleen CFU in these mice when compared with control animals, but marrow CFU were not reduced. These tesults indicate that part of the effect of hypoxemia on CFU may be secondary to the stress of the exposure and suggest that spleen CFU are sensitive to steroid hormones. Further investigation of this and other differences between spleen and marrow CFU could lead to a better understanding of stem cell differentiation.