β- Adrenoceptors activate hepatic glutathione efflux through an unreported pathway

The physiological regulation of hepatic glutathione efflux by catecholamines is poorly understood. The purpose of this work was to review the role of adrenergic receptors (AR) on total glutathione (G_T) efflux in rat liver. Two models were used: isolated hepatocytes and perfused livers. In hepatocytes 10 μM adrenaline (Adr), but not isoproterenol (Iso) a β-AR agonist, or phenylephrine (Phe) an α₁-AR agonist, (in a Krebs-Henseleit buffer (KHB) enriched with Ca²⁺ and some aminoacids) increased in 13% G_T efflux. In livers perfused with KHB, Adr or Iso at 1 μmolar doses (but not Phe) stimulated 11-fold initial velocity of G_T release, but only during the first 2 min of perfusion. This immediate response progressively disappeared during the following 15 min of perfusion. A second phase of G_T efflux, observed between 2 and 14 min of perfusion, mimics the one reported earlier in isolated hepatocytes. The ED₅₀ for Adr and Iso activation are in the range of 320 nM and 10 nM, respectively. Iso-mediated G_T release requires Ca²⁺ to work, and was prevented by H89, glibenclamide, cystic fibrosis transmembrane regulator (CFTR) antibodies, and a direct CFTR inhibitor. This short-lived G_T release system is associated to PKA activation and probably operates through CFTR.