There are numerous studies on transepithelial transports in duct cells including Cl⁣ and/or HCO3⁣. However, studies on transepithelial K⁢ transport of normal duct cells in exocrine glands are scarce. In the present study, we examined the characteristics of K⁢ currents in single duct cells isolated from guinea pig pancreas, using a whole-cell patch clamp technique. Both Cl⁣ and K⁢ conductance were found with KCl rich pipette solutions. When the bath solution was changed to low Cl⁣, reversal potentials shifted to the negative side, ⁣75⁑4 mV, suggesting that this current is dominantly selective to K⁢. We then characterized this outward rectifying K⁢ current and examined its Ca2⁢ dependency. The K⁢ currents were activated by intracellular Ca2⁢. 100 nM or 500 nM Ca2⁢ in pipette significantly (P＜0.05) increased outward currents (currents were normalized, 76.8⁑7.9 pA, n=4 or 107.9⁑35.5 pA, n=6) at ⁢100 mV membrane potential, compared to those with 0 nM Ca2⁢ in pipette (27.8⁑3.7 pA, n=6). We next examined whether this K⁢ current, recorded with 100 nM Ca2⁢ in pipette, was inhibited by various inhibitors, including Ba2⁢, TEA and iberiotoxin. The currents were inhibited by 40.4⁑% (n=3), 87.0⁑% (n=5) and 82.5⁑% (n=9) by 1 mM Ba2⁢, 5 mM TEA and 100 nM iberiotoxin, respectively. Particularly, an almost complete inhibition of the current by 100 nM iberiotoxin further confirmed that this current was activated by intracellular Ca2⁢. The K⁢ current may play a role in secretory process, since recycling of K⁢ is critical for the initiation and sustaining of Cl⁣ or HCO3⁣ secretion in these cells.