Na+-K+-2Cl- co-transporter-mediated fluid secretion increases under hypotonic osmolarity in the mouse submandibular salivary gland.

In this study, the effects of a hypo-osmotic challenge on carbachol (CCh)-induced fluid secretion was investigated using an ex vivo submandibular gland perfusion technique and intracellular pH and Ca(2+) measurements. The osmolality of the perfusion solution was altered to examine the response of the gland to a hypotonic challenge. The flow rate was increased by 34% with a 30% hypotonic solution (225 mOsm), although the Ca(2+) response was unchanged. Lowering the external Cl(-) by 50% abolished this increase in the 30% hypotonic solution. Furthermore, bumetanide, an inhibitor of the Na(+)-K(+)-2Cl(-) co-transporter, completely inhibited the fluid secretion increase caused by the 30% hypotonic solution, and both the total amount of fluid and the flow rate were identical to those of the isotonic solution. This finding was confirmed by measuring Na(+)-K(+)-2Cl(-) co-transporter, bumetanide-dependent NH4(+) transport; Na(+)-K(+)-2Cl(-)- transport was up-regulated more than 40% by a 30% hypotonic challenge. Therefore, the increase in CCh-induced fluid secretion in response to hypotonic conditions can be attributed to a large extent to the specific activation of the Na(+)-K(+)-2Cl(-) co-transporter. PMID: 24623142 [PubMed - as supplied by publisher]
Source: Am J Physiol Renal P... - Category: Urology & Nephrology Authors: Tags: Am J Physiol Renal Physiol Source Type: research