The effect of benzo(a)pyrene on the accumulation of cyclic adenosine 3′,5′-monophosphate (cyclic AMP) in mouse skin in response to isoproterenol has been measured. Topical application of benzo(a)pyrene caused a rise in the basal levels of cyclic AMP and a decreased response to isoproterenol, either injected i.p. or added to a salts medium containing skin pieces. The decreased response was not due to an increased metabolism of isoproterenol. Application of benzo(a)pyrene to the dorsal skin did not increase the basal cyclic AMP levels in the ears; this indicates that the carcinogen does not cause a generalized increase in β-receptor stimulation. The characteristic diurnal fluctuation in epidermal cyclic AMP levels present in untreated mice was not observed after benzo(a)pyrene treatment.

A similar decrease in the isoproterenol stimulation of cyclic AMP occurred after application of croton oil or acetic acid to mouse skin, indicating that the effect was not specific for carcinogens. Acetic acid application did not increase the basal levels of cyclic AMP.

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This work was supported by the University of Adelaide Anti-Cancer Foundation and the Australian Research Grants Committee.

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