Actions of adrenergic agonists on isolated excretory ducts of submandibular glands.

The effects of norepinephrine and isoproterenol on the transepithelial potential difference (PD) and the net transepithelial fluxes of Na, K, Cl, and HCO3 of the main ducts of the submandibular glands of rats and rabbits have been studied by microperfusion of ducts incubated in vitro in an artifical bathing medium. In the rabbit duct, both catecholamines caused depolarization and reduced transepithelial Na reabsorption at concentrations above 10(-29) M. In the rat duct, norepinephrine reduced PD and net Na reabsorption and, in addition, inhibited net K secretion at concentrations of 10(-7) M and above.

Parasympathetic control of Na, K transport in perfused submaxillary duct of the rat.

The effects of stimulating the parasympathetic innervation to rat submaxillary gland on ductal transport of Na, K, water, and transepithelial PD, were tested in the main excretory duct during perfusion through its lumen. During nerve stimulation, transepithelial PD was consistently decreased, usually by about 15 mV, and this decrease could be blocked by atropine but not by adrenergic blocking agents. Net flux of Na, K, or water was not significantly changed during stimulation.

Sympathetic control of Na, K transport in perfused submaxillary main duct of rat.

The effect of stimulating the sympathetic innervation to rat submaxillary gland on ductal transport of Na, K, and water and on transepithelial PD was tested in the main excretory duct during perfusion through its lumen. Stimulation of the sympathetic nerve, supramaximally, caused a decrease of 30-40% in net flux of Na from, and of K to, the lumen in ducts perfused with medium containing Na and K in isotonic concentrations. Net flux of water was unaffected.

Evaluation of a reservoir in the main excretory duct of rat submaxillary gland.

Cannulation of salivary gland main excretory duct at its oral opening is routinely used for collecting fluid, in situ, from the luminally perfused duct, or saliva from the stimulated gland. For perfusion of the main excretory duct, in situ, or for saliva collection, rat submaxillary gland is often the organ of choice, since electrolyte transport occurs at high rates both in the whole gland and in the main excretory duct. Recently, it has been reported that there is a pouchlike dilatation of the main excretory duct at its oral end, and that this dilatation may serve as a fluid reservoir.

Secretion of K and fluid by rat submaxillary during sympathetic nerve stimulation.

Stimulation of the sympathetic innervation to rat submaxillary gland is known to evoke saliva which contains high concentrations of potassium (130-160 meq/liter). Relationships were examined between salivary [K] and several parameters of the stimulation, including pulse frequency and duration of the stimulus train and rate of flow of the evoked saliva. Secretion of sympathetically evoked saliva was found to occur in two phases.