Diurnal variation in cyclic nucleotide levels in normal and phorbol myristate acetate treated mouse epidermis

The diurnal variations in cyclic AMP, cyclic GMP and cyclic GMP/cyclic AMP were determined in mouse epidermis. Slight (60%) diurnal fluctuations were observed in the levels of cyclic AMP and cyclic GMP/cyclic AMP while cyclic GMP showed a more substantial (250%) variation. All 3 parameters showed peaks between 10 AM and 2 PM. The tumor promoter phorbol myristate acetate had no effect on the variation in either cyclic AMP or cyclic GMP, but did appear to reduce the extent of diurnal variation in cyclic GMP/cyclic AMP ratios. The diurnal variation in epidermal mitosis in these mice showed a maximum at 2 PM and a minimum at 10 PM to 2 AM.