Recent studies in our laboratories have shown that Protein Kinase C delta (PKC delta) is essential for insulin-induced glucose transport in skeletal muscle, and that insulin rapidly stimulates PKC delta activity skeletal muscle. The purpose of this study was to examine mechanisms of regulation of PKC delta protein availability. Studies were done on several models of mammalian skeletal muscle and utilized whole cell lysates of differentiated myotubes. PKC delta protein levels were determined by Western blotting techniques, and PKC delta RNA levels were determined by Northern blotting, RT-PCR and Real-Time RT-PCR. Insulin stimulation increased PKC delta protein levels in whole cell lysates. This effect was not due to an inhibition by insulin of the rate of PKC delta protein degradation. Insulin also increased 35 S-methionine incorporation into PKC delta within 5-15 min. Pretreatment of cells with transcription or translation inhibitors abrogated the insulin-induced increase in PKC delta protein levels. We also found that insulin rapidly increased the level of PKC delta RNA, an effect abolished by inhibitors of transcription. The insulin-induced increase in PKC delta expression was not reduced by inhibition of either P13 Kinase or MAP kinase, indicating that these signaling mechanisms are not involved, consistent with insulin activation of PKC delta. Studies on cells transfected with the PKC delta promoter demonstrate that insulin activated the promoter within 5 min. This study indicates that the expression of PKC delta may be regulated in a rapid manner during the course of insulin action in skeletal muscle and raise the possibility that PKC delta may be an immediate early response gene activated by insulin. (c) 2005 Elsevier Inc. All rights reserved.