Cyclic nucleotides in human epidermis--diurnal variations.

In 12 healthy, adult males, the epidermal content of both cAMP and cGMP was determined radioimmunologically every 6 h over a period of 30 h, avoiding any ischemia, which can alter unphysiologically the in vivo levels of epidermal cyclic nucleotides. For cAMP a diurnal fluctuation with maximal level at midnight could be proved (p less than 0.05), whereas cGMP, in contrast to experiments in mice, revealed no significant variation during the test period. The presented results describe for the first time the diurnal course of human epidermal cGMP.