Glucocorticoids specifically increase Kv1.5 K+ channel mRNA in normal and clonal (GH3) rat pituitary cells. Here, we demonstrate that dexamethasone, a glucocorticoid agonist, rapidly induces Kv1.5 gene transcription, but does not affect Kv1.5 mRNA turnover t 1 2 ≈ 0.5 hr) in GH3 cells. Immunoblots indicate that the steroid also increases the expression of the 76 kd Kv1.5 protein 3-fold within 12 hr without altering its half-life (t 1 2 ≈ 4 hr). In contrast, Kv1.4 protein expression is unaffected. Finally, we find that the induction of Kv1.5 protein is associated with an increase in a noninactivating component of the voltage-gated K+ current. Our results indicate that hormones and neurotransmitters may act within hours to regulate excitability by controlling K+ channel gene expression.
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