A single injection of isoproterenol (1.0 µmole/gm body weight) produces a marked increase in DNA synthesis and cellular proliferation in mouse salivary gland. The activity of thymidine kinase and α-amylase was determined in the time interval between injection of isoproterenol and the peak of DNA synthesis, both under optimal conditions of stimulation and under conditions that modify the gland's proliferative response to isoproterenol. Thymidine kinase activity was found to parallel changes in DNA synthesis and to be sensitive to low doses of Dactinomycin (0.08 µg/gm body weight.) Conversely, α-amylase activity varied independently of DNA synthesis and was resistant to low doses of Dactinomycin.

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This work was supported by USPHS Research Grants CA-08373 and CA-07174 from the National Cancer Institute.

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