Sodium reabsorption: diffusion of a solute from one bath to the other requires, a concentration gradient, a pore or channel permeable to that solute. Substances normally reabsorbed into the blood by energy and the na+-dependant mechanism protects against loss of important organic nutrints: e. g. Symport carriers: na-glucose co-transporter: there is a max capacity of cotransports= if they are maxed out, the remaining glucose will be excreted out. Chlorine uptake: chloride ions are absorbed down the electrical gradient created by active reabsorption of na+ through the tight junctions. If you blocked the na-k transporter, na+, cl, amino acid, glucose reabsorption decreases, Urine excretion & h20 handling: normal ecf osmolarity = 300 mosm/litre. Kidneys can produce concentrated or dilute urine: ability to do this is due to the functional anatomy of juxtaglomerular nephones and their lloh. Comcnetration of na ions diminishes in tubular fluid and it increases in lateral spaces. This induces water to flow into the lateral sapces.