The effect of a three-week treatment regimen with suramin (30, 60 or 90 mg/kg body weight) on the cell proliferation of small intestinal crypts and dorsal epidermis of the nude mouse was studied using standard auto-radiographic methods after in vivo pulse labeling with H-3-thymidine. Suramin was slightly toxic to the animals in a dose-dependent manner (p<0.01) as measured by the decrease of the rate of weight gain of the treated animals. In the small intestine suramin treatment led to crypt shrinkage (factor: about 70-80%; p<0.05) mainly by increasing the rate of cell loss out of the crypt epithelium (p<0.05) and to a lesser degree by inhibiting the proliferation of crypt cells. However, this suramin treatment scheme did not significantly affect the H-3-thymidine labeling index and the mitotic index of the basal cell layer of the epidermis. The present findings indicate that suramin can be used to approach the problem of differential homeostatic reactions of epithelial tissue renewal in vivo.

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