Further studies on adenyl cyclase in psoriasis

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Abstract
Slices of human skin obtained with-a keratome were pre-incubated with [3H]adenine to label the ATP pool from which cyclic AMP was subsequently formed. The accumulation of radioactive cyclic AMP was measured as an index of adenyl cyclase activity. The data showed that both the ability to incorporate [3H] into ATP and adenyl cyclase activity were significantly lower in psoriatic plaques than in uninvolved skin of the psoriatic patients, or in normal skin of control subjects. The response of adenyl cyclase to the stimulation of 3.3 μM adrenaline was less than five fold in psoriatic plaques as compared to twelve to thirty-two fold in the uninvolved skin. The response to the stimulation of prostaglandin E2 (5 μg/ml) showed no significant difference between the plaque and normal skin. The adenyl cyclase activity in uninvolved skin of psoriatic patients appeared normal. Propranolol (10 μM) blocked the stimulatory effect of adrenaline but not that of PGE2 in normal skin. These resulsuggest that the adenyl cyclase system of the skin has different regulatory sites for adrenaline and PGE2, and that the enzyme is defective in the epidermis of the psoriatic plaque, especially at the adrenaline regulatory site. A preliminary report on this study was given at the Second International Conference on Cyclic AMP at Vancouver, Canada, 8-11 July 1974.