Reports of the effects of beta-adrenergic receptor blocking agents on the proliferative activity of rat jejunal crypt cells are contradictory. According to Tutton and Helme (1974) a single injection of propranolol or practolol (10 mg/kg) increased the mitotic index twofold and shortened the duration of the cell cycle of the crypt cells. However, upon repeating the experiments with double the dose of propranolol, Maurer-Schultze et al. (1986) observed no such effects using cell kinetic methods with 3H-thymidine instead of the stathmokinetic method applied by Tutton and Helme. Since the discrepancy in the results may have been due to methodological differences the same stathmokinetic method used by Tutton and Helme has been applied in the present work. However, the results obtained with this method indicate no influence by propranolol on the proliferation of jejunal crypt cells even with a dose of 20 mg/kg. Consequently we were unable to confirm the stimulant effect of propranolol on crypt cell proliferation. The possible causes of the discrepancy between the present results and those of Tutton and Helme are discussed.
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