Tubules reabsorption

Agent Uptake by bone Intestinal absorption Kidney tubule reabsorption Fecal excretion... 

In the distal tubule, reabsorption is entirely transcellular, and is regulated by parathyroid hormone and calcitriol (increasing reabsorption) and calcitonin (reducing reabsorption). 

In children with lead encephalopathy, proximal tubule reabsorptive defects characterized by the Fanconi syndrome have been observed [13]. The Fanconi syndrome appears when blood lead levels approach 150 //g/ dL. It is rapidly reversed by chelation therapy designed to treat the far more dangerous lead encephalopathy. The proximal tubule reabsorptive defect can regularly be induced experimentally in rats fed dietary lead [14]. In both children and experimental animals, acute lead nephropathy is consistently associated with acid-fast intranuclear inclusions in proximal tubule... 

Increased proximal tubule reabsorption of solutes and water -... 

Ociasionally. a patient may experience hypercalcemia or liypcr-uiicemia after long-term use of a thia/idc or thia/idc-like diuretic. Tliis results from diuretic-induced reduction of the pti-irem s plasma volume and a concomitant compeasulory increase in the proximal tubule reabsorption of luminal fluid and solutes. In such a situation, mote Ca and uric acid than usual will be reabsorbed proximally. The seriousness of these two adverse cffccLs depends in part on the duration and extent of the plasma volume r uction. 

The measured value of CLr can then be compared to OfdFR to determine whether tubule secretion or tubule reabsorption play significant roles in the urinary excretion of the drug. 

It has been suggested that bumetanide inhibits renal cAMP. This could affect tubule reabsorption. 

There are many examples in mammalian cells in which the effectuation of hormone action is associated with variations in calcium concentration in the different cellular compartments. Such hormonal actions include stimulation of corticosteroid secretion in the adrenal, the effect of parathyroid hormone on renal tubules, reabsorption and release of calcium from the bone, the effect of melanocyte hormone on melano-phores, the stimulation of smooth muscle contraction by acetylcholine and its retraction by epinephrine, the effect of epinephrine on heart contraction, etc. The role of calcium in the sequence of steps following the hormonal stimulus is often difficult to interpret. 

Sodium is reabsorbed in the proximal and the distal tubules. A major fraction of filtered sodium and water is reabsorbed in the proximal tubule. Reabsorption is isotonic, and consequently the sodium concentration in the proximal tubule is not markedly changed. However, sodium reabsorption in the proximal tubule is not passive. A number of experiments have suggested... 

Birn, H., Willnow, T. E., Nielsen, R., Norden, A. G., Bonsch, C., Moestrup, S. K., Nexo, E., Christensen, E. I. 2002. Megalin is essential for renal proximal tubule reabsorption and accumulation of transcobalamin-B(12). Am J Physiol Renal Physiol, 282, F408-16. Burger, R. L., Schneider, R. J., Mehlman, C. S., Allen, R. H. 1975. Human plasma R-type vitamin B 12-binding proteins. II. The role of transcobalamin I, transcobalamin III, and the normal granulocyte vitamin B 12-binding protein in the plasma transport of vitamin B12.J Biol Chem, 250, 7707-13. 

The outer medulla is particularly sensitive to hypoxia because the active reabsorption process within the thick ascending loop of Henle requires a high level of oxygen consumption (Brezis and Rosen 1995). Therefore, decreased medullary blood flow or increased tubule reabsorption may induce medullary hypoxia and secondary ischemia. 

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