Effects of adrenergic agonists on electrolyte transport in perfused salivary duct of rat.

The Na and Cl absorption and K secretion that occur in the main duct of rat submandibular gland are affected by adrenergic actions. The specific effects of stimulation of alpha-, beta 1- and beta 2-adrenergic receptors on net transepithelial fluxes of Na, K and Cl were investigated in microperfused main excretory duct of rat submandibular gland. Administration of methoxamine (2.5 micrograms . kg-1 . min-1, i.v.) resulted in marked decreases in net efflux (or absorption) of Na (38%) from the duct into the interstitial fluid and net influx (or secretion) of K (20%) from interstitial fluid into the ductal lumen without any effect on net efflux or reabsorption of Cl. A higher dose of methoxamine (5 micrograms . kg-1 . min-1, i.v.) produced further inhibition of net fluxes of Na and K without affecting net flux of Cl. Dobutamine (50 micrograms . kg-1 . min-1, i.v.) enhanced net effluxes of Na (40%) and Cl (300%) from the lumen but did not alter net K influx into the lumen. When the dosage of dobutamine was increased to 200 micrograms . kg-1 . min-1, an inhibition of net influx of K (28%) into ductal fluid was observed in addition to enhanced net fluxes of Na and Cl from the lumen. Administration of terbutaline (15 and 30 micrograms . kg-1 . min-1, i.v.) decreased net influx of K (30-40%) and increased net efflux of Cl (280%) without affecting net efflux of Na.(ABSTRACT TRUNCATED AT 250 WORDS)