Abstract: Objective To study the mechanism of abnormal proliferation of keratinocytes in psoriasis. Methods The activity of tyrosine protein kinase (TPK) in the keratinocytes of lesional skin in progressive stage was assayed by phosphorylation of exogenous substrates. Results The basic activity of TPK and autophosphorylation of transforming growth factor(TGF) receptor were significantly increased in the psoriatic lesions in progressive stage.The TPK activity of epidermal growth factor(EGF)-receptor was also significantly increased in the psoriatic lesions after stimulation of TGF-alpha as compared with normal control.There was a positive correlation between the activity of TPK and expression of EGFR in the psoriatic keratinocytes. Conclusions The increased activity of TPK and the high reactivity to the stimulation of growth factors are important in the hyperproliferation of psoriatic keratinocytes.The change of the activity of TPK may result from increased expression of EGF receptors. EGF receptors probably play an important role in keratinocyte hyperproliferation of psoriasis.

Key words: Psoriasis, Protein-Tyrosine kinase, Receptors, epidermal growth factor-urogastrone, Transforming growth factor alpha