Enhancement of colony-stimulating activity production by lithium.

Since lithium causes granulocytosis in some patients, its effect upon granulocyte production was investigated using mouse marrow in the agar culture system. When lithium was added to semisolid cultures of mouse marrow, there was no stimulation of colony formation in the absence of colony-stimulating activity (CSA). In addition, lithium did not potentiate the action of already formed CSA. However, lithium did stimulate the production of CSA by lung tissue. Lithium enhancement of CSA production was blocked by puromycin, indicating that lithium action required active new protein synthesis. It was concluded that lithium promoted enhanced granulocyte production in vitro by stimulating the synthesis of CSA.