Osmotic flow transients during acetylcholine stimulation in the perfused rat submandibular gland

Abstract

SUMMARYOsmotic stress was applied to the perfused rat submandibular gland during steady-state fluid secretion. Alterations of perfusate osmolarity, by addition or withdrawal of sucrose or NaCi, caused transient changes in secretory rate during continuous stimulation with I /LM acetylcholine (ACh). Hyposmotic perfusates transiently increased, and hyperosmotic perfusates transiently reduced, the secretory rate. The transients were attributed to changes in osmotic flow resulting from changes in the instantaneous transepithelial osmotic gradient. The time course of the change in interstitial osmolarity was determined by using a Cl-electrode to record the changes in interstitial Cl-concentration following a step change in perfusate Cl-concentration. From the calculated changes in interstitial osmolarity and the resulting changes in secretory rate, the osmotic

Cotransport of water by the Na+-K+-2Cl−cotransporter NKCC1 in mammalian epithelial cells

“…Given the estimated coupling ratio and typical values for intracellular and extracellular ion activities, it can be calculated that under physiological conditions NKCC1 is capable of transporting water against an osmotic gradient of the order of 100 mosmol l −1 (Zeuthen, 2010). This is consistent with the uphill water transport demonstrated in a variety of salivary glands (Ludwig, 1861; Imai et al 1973; Nakahari et al 1997; Murakami et al 2006).…”

Real Time Measurements of Water Flow in Amphibian Gastric Glands

“…Chloride ions are involved in the formation of the osmotic gradient in a large number of tissues, from salivary glands (73) to choroid plexus epithelium (74) to cholangiocytes (75). Recently, parchorin, a novel protein with significant homology to the family of chloride intracellular channels, has been cloned and characterized in the apical membrane of rabbit parietal cells (76).…”

Apical maxi-K (KCa1.1) channels mediate K+ secretion by the mouse submandibular exocrine gland

“…To investigate the relationship of [K ϩ ] and of [Na ϩ ] to flow rate in the mouse submandibular gland, we used the ex vivo, perfused gland preparation. The secretion rate, as previously described in rat submandibular glands (23), decreases when the osmolality of the perfusate is increased by the addition of sucrose. Figure 5A shows that, in the mouse submandibular, fluid secretion decreased 71.5 Ϯ 3.8% when the perfusate was made ϳ30% hypertonic by the addition of 100 mM sucrose.…”