β‑Adrenergic Stimulation of Short‑Circuit Currents in Human Intestinal Epithelial Caco‑2 Cells

To investigate the effects of epinephrine on ion transport of intestinal epithelia short‑circuit cur‑ rents (Isc in monolayers of Caco‑2 cells grown on permeable membrane supports were measured in the Ussing chamber. The application of epinephrine to the basolateral solution produced a transient increase of Isc (maximal currents induced by 5 µM and more of epinephrine. The value of the peak current was 3.4 µA / 2 . Isoproterenol (a β‑agonist increased Isc in a manner analogous to epinephrine application but phen‑ ylephrine (an α 1‑agonist induced no Isc change. Clonidine (an α 2‑agonist transiently decreased Isc by about 0.8 µA/ 2 at a high dose of 100 µM. The Isc increase induced by epinephrine or isoproterenol was mim‑ icked by a membrane‑permeable cyclic AMP analogue dibutyryl cyclic AMP or a calcium ionophore A 23187. Verapamil a calcium channel blocker eliminated the epinephrine‑induced Isc increase and 5‑nitro‑2‑ (3‑phenylpropylamino benzoic acid (NPPB a chloride channel blocker reduced the Isc increase. These ob‑ servations suggest that in Caco‑2 epithelia ( epinephrine induces Isc increase via β‑adrenergic receptors and ( the epinephrine‑induced Isc responses have at least two components namely verapamil‑sensitive Ca 2+ and NPPB‑sensitive Cl - transports.