Glycogen Turnover in Epidermis

To the Editor.—  A recent publication by Halprin et al¹ aided the understanding of epidermal glycogen metabolism. Space limitations preclude the rigorous discussion of rationale that this report deserves, but several points require clarification.Adenosine-3′, 5′-cyclic monophosphoric acid (cyclic AMP) and theophylline were mentioned in the "Material and Methods," section, but there is no further reference to their use. The source of a α-glucosidase was not reported; as we noted recently,² purified enzyme is available from Boehringer Mannheim Corp (No. 15043 EAAU). In our hands, there is no need to augment this preparation with α-amylase to obtain quantitative glycogen hydrolysis. The reference to Huijing³ for glycogen assay details applies only to the glucosidase incubation step, since he detected glucose with glucose oxidase, and Halprin et al employed a fluorometric hexokinase-based assay.The comment that 0.2-mm keratome slices of normal and psoriatic skin contained about 85% epidermis is