Determination of cyclic AMP in heat-separated human epidermal tissue

Heat separation is introduced as a simple, reliable and quick method for obtaining pure epidermis for cyclic AMP analysis. Heating at 60 degrees -65degrees C for 10 min resulted in a distinct separation of epidermis from dermis. The level of cyclic AMP in epidermal tissue from 9 patients was 3.93 +/- 0.31 pmol per mg dry weight. The inter- and intra-assay variations were 10.3% and 8.8%, respectively. The coefficience of variation in eight biopsies from the same piece of skin was 16.2% The sensitivity of the assay was 0.07 pmol. Recovery analyses revealed that 80.5% of labelled cyclic AMP was refound after extraction and purification procedures. Addition of unlabelled cyclic AMP resulted in a recovery of approximately 100%. The specificity of the assay was high without interference from several nucleotides and the validity was confirmed by zero values obtained after addition of phosphodiesterase or charcoal.