Glucose then exits basolaterally via a facilitated diffusion glucose transport pathway (GLUT-2). In between meals, when nutrients are not available, water absorption can alternatively be driven by the coupled uptake of chloride and sodium across the apical membrane via the downregulated in adenoma (DRA) chloride/bicarbonate exchanger and the sodium/hydrogen exchanger (NHE-3), respectively . Again, this process is dependent on the Na+/K+-ATPase and probably also involves basolateral chloride exit across a potassium/chloride cotransporter (putatively identified as KCC1).
Considering fluid secretion, chloride uptake from the bloodstream across the basolateral membrane of crypt epithelial cells is mediated by a sodium/potassium/2 chloride cotransporter, NKCC1, which responds to the low intracellular sodium concentration established by the sodium pump.
Potassium accumulated within the cytosol is recycled across the basolateral membrane via specific channels, whereas chloride exits the cell apically, via either cystic fibrosis transmembrane conductance regulator (CFTR) chloride channels or possibly (in lesser amounts) via additional chloride channels, such as the CLCA channels that are regulated by calcium. Both potassium and chloride channels serve as control points for the regulation of secretion, and can be activated by specific second messengers, such as cAMP, cGMP and calcium. Interestingly, cAMP has also been shown to inhibit NHE-3. You will always find the required amount of cialis professional online at the pharmacy that will be happy to take best care of you by offering safe possibility to purchase the drugs you need without any need to get a prescription first or take any other extra steps.