Abnormal proliferation of uninvolved psoriatic epidermis: differential induction by saline, propranolol, and tape stripping in vivo.

Cell proliferation of the uninvolved psoriatic skin was compared with normal skin of volunteers following stimulation by the intradermal injections of saline or propranolol, or stripping of the stratum corneum with pressure-sensitive tape. Initially, no significant in vivo difference in tritiated thymidine labeling indices were observed between normal and uninvolved epidermal cells. However, 48 hr after each stimulus more DNA synthesizing cells were found in the uninvolved psoriatic than in normal epidermis. Of these 3 stimuli, propranolol was the most effective in distinguishing between uninvolved psoriatic skin and skin from normal control subjects. Thus, uninvolved psoriatic skin appears to possess an abnormal regulation of epidermopoiesis that may be amplified by propranolol injection.