Our previous study indicated that TGF-beta 1 induced the expression of a transient outward K+ channel (A-type) during the phenotypic transformation of vascular fibroblasts to myofibroblasis. Here, we studied the relevant signal transduction pathway using whole cell recording and a quantitative RT-PCR technique. Results indicate that the protein kinase C (PKC) agonist phorbol-12-myristate-13-acelate (PMA, 1 mu M) could mimic the effect of TGF-beta 1 (20 ng/ml) on the expression of an A-type K+ channel and induced a similar A-type K+ current. Moreover, a PKC inhibitor, bisindolylmaleimide 1 (1 mu M), could abrogate the effect of TGF-beta 1 on K(V)4.2 expression. This result suggests that a PKC pathway may be involved in the expression of an A-type K+ channel induced by TGF-beta 1 in rat vascular myofibroblasts. (c) 2005 Elsevier Inc. All rights reserved.