Inhibition of epidermal adenyl cyclase by lithium carbonate.

An in vitro floating system was used to investigate the effect of lithium carbonate (Li2CO3) on the activity of adenyl cyclase in normal pig epidermis. Li2CO3 decreased the responsiveness of adenyl cyclase to stimulation by histamine, adenosine monophosphate (AMP) and epinephrine. This abnormality is similar but not identical to the previously described impaired responsiveness of adenyl cyclase to epinephrine and PGE2 in psoriatic plaques compared to normal adjacent skin. Involved and uninvolved skin from a psoriatic on lithium therapy demonstrated decreased responsiveness to in vitro stimulation by epinephrine, histamine and adenosine when compared to skin from psoriatics who were not on lithium therapy. These results are consistent with the observation that lithium therapy worsens psoriatic lesions.