Yes
Fluid in the filtrate entering the proximal convoluted tubule is reabsorbed into the peritubular capillaries. This is driven by sodium transport from the lumen into the blood by the Na+/K+ ATPase in the basolateral membrane of the epithelial cells. Sodium reabsorption is primarily driven by this P-type ATPase. It is termed reabsorption because the fluid and other substances that are reabsorbed from the bloodstream through the glomerulus into Bowman's capsule, which leads to the peritubular capillaries. This happens as a result of sodium transport from the lumen into the blood by the Na+/K+ ATPase in the basolateral membrane of the epithelial cells. Thus, the glomerular filtrate becomes more concentrated, which is one of the steps in forming urine. 1 A large amount of fluid is cycled through the bowel each day. ( 2 net reabsorption = 98%) Intestinal fluids are isotonic. 3  Water is reabsorbed passively down its osmotic gradient created by the active reabsorption of nutrients and electrolytes. About 1500 mls/day enter the colon from the ileum. This means that over a litre per day is absorbed in the colon. The intestinal contents are essentially isotonic by the time the jejunum is reached because water can move into or out of the intestine in response to any osmotic gradient. The luminal surface of the epithelial cells of this segment of the nephron is covered with densely packed microvilli forming a border readily visible under the light microscope giving the brush border cell its name. This is driven by sodium transport from the lumen into the blood by the Na+/K+ ATPase in the basolateral membrane of the epithelial cells. Sodium reabsorption is primarily driven by this P-type ATPase. In summary: 1  A large amount of fluid is cycled through the bowel each day. ( 2 net reabsorption = 98%) Intestinal fluids are isotonic. 3  Water is reabsorbed passively down its osmotic gradient created by the active reabsorption of nutrients and electrolytes. About 1500 mls/day enter the colon from the ileum. This means that over a litre per day is absorbed in the colon. The intestinal contents are essentially isotonic by the time the jejunum is reached because water can move into or out of the intestine in response to any osmotic gradient. The ingestion of isotonic saline causes an isotonic expansion of ECF volume without expansion of ICF volume. This is followed by a baroreceptor mediated increase in renal excretion of Na + and water to restore ECF volume to normal. The effect of ingesting 4 L of isotonic saline in the average 70 Kg adult male is illustrated in the figure which shows a proportional distribution of the 4 L of saline between the ISF and the PV. About 98% of this fluid is reabsorbed resulting in a faecal water loss of only 200 mls/day. This reabsorption occurs predominantly in the jejunum and ileum. About 1500 mls/day enter the colon from the ileum. This means that over a litre per day is absorbed in the colon. The intestinal contents are essentially isotonic by the time the jejunum is reached because water can move into or out of the intestine in response to any osmotic gradient. Definition. Dehydration is an ambiguous term that does not distinguish between simple water loss and loss of Na+. Both water loss and Na+ loss are associated with a decrease in the ECF volume, which is determined by the amount of Na+ in the body and not by the Na+ concentration in the plasma. 1. Isosmotic dehydration. Decreased renal water excretion. 1. Decreased glomerular filtration rate. 2. Increased proximal tubular reabsorption. Decreased renal perfusion pressure in diseases such as congestive heart failure, cirrhosis, nephrotic syndrome stimulates proximal tubular reabsorption. 3. The figure at right summarizes water reabsorption along the nephron. Water reabsorption is a passive process: water is reabsorbed by osmosis. In most of the nephron, water reabsorption is unregulated and coupled to solute reabsorption. The ability to excrete urine that is more concentrated than the extracellular fluid (ECF) depends on the creation of a hyperosmotic environment in the medulla. As the collecting duct descends through the medulla, the increasing osmolarity in the interstitial fluid drives water reabsorption. However, there is a tremendous variability in water excretion. The urine produced can be either concentrated, or very dilute
https://en.wikipedia.org/wiki/Proximal_convoluted_tubule https://en.wikipedia.org/wiki/Reabsorption http://www.anaesthesiamcq.com/FluidBook/fl3_5.php https://en.wikipedia.org/wiki/Proximal_convoluted_tubule http://www.anaesthesiamcq.com/FluidBook/fl3_5.php http://humanphysiology.tuars.com/program/section7/7ch09/7ch09p24.htm http://www.anaesthesiamcq.com/FluidBook/fl3_5.php http://physiology.lf2.cuni.cz/teaching/lecturenotes/elektrolytes/ http://courses.washington.edu/conj/bess/water/water.htm
fluid reabsorption is isotonic