α- and β-Adrenergic Effects on Na,K,Cl,and HCO 3 Transport in Perfused Salivary Duct during Sympathetic Nerve Stimulation 1

Summary

Effects of stimulation of α- and β-adrenergic receptors on transport of Na, K, and Cl by ductal epithelial cells were studied in luminally perfused main excretory duct of rat submaxillary gland with isotonic bicarbonate-saline solution. Either phenoxybenz-amine or propranolol (5 mg/kg body wt) was given i.p. 25 min prior to the stimulation of the sympathetic innervation to the gland. Stimulation of the sympathetic nerve in the presence of phenoxybenzamine decreased net Na and K fluxes by 26 and 39%, respectively, while net efflux of Cl was increased by 70% and net influx of HCO₃ about 65%. Stimulation of the sympathetic nerve in the presence of propranolol caused a decrease of 39% in net efflux of Na and a decrease of 32% in net influx of K; no changes in net flux of Cl and HCO₃ were observed. Stimulation of the sympathetic nerve modifies electrolyte transport by duct cells, and present work shows that a reduction in net fluxes of Na and K can be induced by either α- or β - adrenergic stimulation. There was, however, a distinct difference between effects of α- and β-adrenergic receptors on net fluxes of Cl and HCO₃. Thus, activation of β-adrenergic receptors enhanced net Cl efflux, and net HCO₃ influx, whereas no changes in net flux of Cl and HCO₃ were oberved with α-adrenergically evoked responses.