The rapid regulation of sweat production under conditions of acute changes in hormonal levels, highlights the importance of an understanding of rapid responses to hormones, and the signaling mechanisms involved. Hormonal effects of sweat production are observed at circulating levels of the hormones and thus the study of rapid effects is physiologically relevant. NCL-SG3 cells are an ion transporting human epithelial cell line established by Simian virus 40(SV40) infection of primary cultures from eccrine sweat glands (Lee & Dessi.1989). These cells are used here as a model to study signaling cascades in the human eccrine sweat gland.The direct binding and activation of different PKC isoforms by various steroid hormones has been well documented, however in the sweat gland epithelia the mechanism of action is still being established. PKA was measured to determine whether the cAMP-dependent signal transduction pathway is involved in the response to Estradiol in NCL-SG3 cells. Protein kinase C activation was detected using standard Western blotting techniques. PKA activation was measured using the PepTag Assay^TM for non-radioactive detection of cAMP- dependent protein kinase (PKA).A rapid, two fold increase in the activation of the protein kinase C isoforms α, δ and ε was seen after 5 minute treatment with 10nM 17β-estradiol. This increase returned back to basal activation levels after a further 5 minutes. A similar rapid effect of 17β-estradiol was observed when PKA activation was measured (<7minutes) in NCL-SG3 cells.The various PKC isoforms have subtly different kinetics and modes of activation. The fact that we have seen a rapid activation by estrogen of both classical, as well as novel PKC isoforms, potentially implicates several downstream targets of the sex steroids in the human eccrine sweat gland. An estrogen induced PKCδ-specific activation of adenylyl cyclase activity, which results in an increase in PKA activity has been demonstrated in epithelial cells (Harvey et al. 2002). Cross-regulation of PKCδ and ε has previously been shown in cardiomyocytes (Rybin et al. 2003). A corresponding mechanism whereby the activation of PKCδ is coupled to that of PKCε,may also exist in sweat gland epithelial cells. Preliminary work suggests the involvement of PKA as a potential downstream target in the signal transduction pathway for the non-genomic action of estrogen, which in turn mediates secretion and absorption in epithelial cells.