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

K+- and Na+-selective double-barrelled microelectrodes were used for intrac ellular and luminal measurements in salivary ducts of Periplaneta americana . The salivary ducts were stimulated with dopamine (10(-6) mol l(-1)). Dopa mine 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 unstimulat ed 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 (PDb) was depolarized from -65+/-6 mV to -31+/-13 mV (n=12) and the transepithelial potential di fference (PDt) was hyperpolarized from -13+/-6 mV to -22+/-7 mV (n=22, lume n negative) upon stimulation with dopamine. The re-establishment of prestim ulus values of intracellular [K+] and [Na+] and PDb was inhibited by basola teral 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 PDb. We prop ose a model for dopamine-stimulated ion transport in the salivary ducts inv olving basolateral Na+-K+-2Cl(-) cotransport and active extrusion of K+ via the apical membrane. (C) 2001 Elsevier Science Ltd. All rights reserved.