Dopamine-induced epithelial K + and Na + movements in the salivary ducts of Periplaneta americana

K +- and Na +-selective double-barrelled microelectrodes were used for intracellular and luminal measurements in salivary ducts of Periplaneta americana. The salivary ducts were stimulated with dopamine (10 −6 mol l −1). Dopamine decreased intracellular [K +] from 112±17 mmol l −1 to 40±13 mmol l −1 ( n=6) and increased intracellular [Na +] from 22±19 mmol l −1 to 92±4 mmol l −1 ( n=6). Luminal [K +] was 15±3 mmol l −1 in the unstimulated salivary ducts and increased to 26±11 mmol l −1 upon stimulation with dopamine ( n=10). Luminal [Na +] was insignificantly increased from 105±25 mmol l −1 to 116±22 mmol l −1 ( n=12) by stimulation with dopamine. The potential difference across the basolateral membrane (PD b) was depolarized from −65±6 mV to −31±13 mV ( n=12) and the transepithelial potential difference (PD t) was hyperpolarized from −13±6 mV to −22±7 mV ( n=22, lumen negative) upon stimulation with dopamine. The re-establishment of prestimulus values of intracellular [K +] and [Na +] and PD b was inhibited by basolateral addition of ouabain (10 −4 mol l −1). Furosemide (10 −4 mol l −1) in the bath inhibited the dopamine-induced increase in intracellular [Na +], the decrease in intracellular [K +] and the depolarization of PD b. We propose a model for dopamine-stimulated ion transport in the salivary ducts involving basolateral Na +-K +-2Cl − cotransport and active extrusion of K + via the apical membrane.