Maturation of rat proximal tubule chloride permeability

Baum, Michel; Quigley, Raymond

doi:10.1152/ajpregu.00257.2005

Cited by 19 publications

(17 citation statements)

References 36 publications

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“…Thus there is a maturational decrease in proximal tubule P Na /P Cl and increase in P HCO3 /P Cl . This indicates that there is a maturational change in the paracellular pathway in mice as we have previously found in rabbits and rats (8,37,43).…”

Section: Resultssupporting

confidence: 82%

“…Neonatal rabbit tubules had a lower chloride and bicarbonate permeability, a higher resistance and a higher P Na /P Cl and P HCO3 /P Cl than the adult segment (35,37,43). We have recently demonstrated developmental changes in the rat proximal tubule perfused in vitro showing that maturational changes in proximal tubule permeability are not limited to the rabbit (8). While direct measurement of ion permeability is not technically possible in neonatal mice, we were able to measure P Na /P Cl and P HCO3 /P Cl and found developmental proximal tubule changes between ϳ10-day-old and adult mice as we have previously described in rabbits and rats (7,35,37,43).…”

Section: Discussionmentioning

confidence: 95%

“…Studies showing a maturational difference in permeability of the paracellular pathway have previously been performed in rabbit and the rat (8,37,43). To determine whether there was a change in the permeability properties of the paracellular pathway in the mouse, we examined the relative permeability of ions using dilution potentials, a well-described characteristic of the paracellular pathway.…”

Section: Resultsmentioning

confidence: 99%

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Claudins 6, 9, and 13 are developmentally expressed renal tight junction proteins

Abuazza¹,

Becker²,

Williams³

et al. 2006

American Journal of Physiology-Renal Physiology

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106

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The adult proximal tubule is a low-resistance epithelium where there are high rates of both active transcellular and passive paracellular NaCl transport. We have previously demonstrated that the neonatal rabbit and rat proximal tubule have substantively different passive paracellular transport properties than the adult proximal tubule, which results in a maturational change in the paracellular passive flux of ions. Neonatal proximal tubules have a higher PNa/PCl ratio and lower chloride and bicarbonate permeabilities than adult proximal tubules. Claudins are a large family of proteins which are the gate keepers of the paracellular pathway, and claudin isoform expression determines the permeability characteristics of the paracellular pathway. Previous studies have shown that claudins 1, 2, 3, 4, 5, 7, 8, 10, 11, 12, 15, and 16 are expressed in the adult mouse kidney. To determine whether there are developmental claudin isoforms, we compared the claudin isoforms present in the neonatal and adult kidney using RT-PCR to detect mRNA of claudin isoforms. Claudin 6, claudin 9, and claudin 13 were either not expressed or barely detectable in the adult mouse kidney using traditional PCR, but were expressed in the neonatal mouse kidney. Using real-time RT-PCR, we were able to detect a low level of claudin 6 mRNA expression in the adult kidney compared with the neonate, but claudin 9 and claudin 13 were only detected in the neonatal kidney. There was the same maturational decrease in these claudin proteins with Western blot analysis. Immunohistochemistry showed high levels of expression of claudin 6 in neonatal proximal tubules, thick ascending limb, distal convoluted tubules, and collecting ducts in a paracellular distribution but there was no expression of claudin 6 in the adult kidney. Using real-time RT-PCR claudin 6 and 9 mRNA were present in 1-day-old proximal convoluted tubules and were virtually undetectable in proximal convoluted tubules from adults. Claudin 13 was not detectable in neonatal or adult proximal convoluted tubules. In summary, we have identified developmentally expressed claudin isoforms, claudin 6, claudin 9, and claudin 13. These paracellular proteins may play a role in the maturational changes in paracellular permeability.

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Section: Resultssupporting

confidence: 82%

Section: Discussionmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Claudins 6, 9, and 13 are developmentally expressed renal tight junction proteins

Abuazza¹,

Becker²,

Williams³

et al. 2006

American Journal of Physiology-Renal Physiology

Self Cite

106

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“…Whether chloride is absorbed or sodium is secreted is dependent on the relative permeabilities of chloride to sodium in the proximal tubule. The relative chloride to sodium permeability is higher in the adult than the neonate, so passive chloride transport secondary to the lumen-negative potential difference in the early proximal tubule does not occur to a significant degree in the neonate [14,195]. The reabsorption of bicarbonate in preference to chloride by the early proximal tubule causes the luminal fluid in the late proximal tubule to have a higher chloride and lower bicarbonate concentration than that of the peritubular fluid [196,197].…”

Section: Development Of Proximal Tubule Nacl Transportmentioning

confidence: 99%

“…There are also changes in the properties of the paracellular pathway during postnatal development [14,195,210,211]. Most importantly, the permeability of the proximal tubule to chloride ions is less in the neonate than the adult [14,195,211].…”

Section: Development Of Proximal Tubule Nacl Transportmentioning

confidence: 99%

Renal Tubular Development

Baum

2014

Pediatric Nephrology

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The nephron is faced with the enormous task of maintaining a constant composition and volume of the extracellular fluid. The amount of electrolytes and water ingested and absorbed must be eliminated, and the waste products from metabolism must also be excreted. This challenge is all the more complex as our dietary intake is quite variable from day to day. Despite this variable intake, there is virtually no change in the volume or composition of the extracellular fluid volume from day to day.There are two possible ways that our kidney could balance ingestion and excretion. The kidney could be a secretory organ where all the excess solutes and water ingested would be excreted by tubular secretion. This would be very inefficient and require an enormous amount of energy. In addition, in times of a disturbance in the extracellular fluid volume such as a high salt intake or volume loss from diarrhea, the regulatory systems necessary to maintain a constant extracellular fluid volume and composition while excreting waste products would be very complex. On the other hand, the kidney could filter an enormous quantity of extracellular fluid, which would be very efficient in removing waste products, and reclaim the desired salt, organic solutes, and water. With volume depletion, a greater fraction of salt and water could be reabsorbed, and when one has a dietary indiscretion such as the salt intake from a pepperoni pizza, there could be a reduction in sodium reabsorption leading to an increase in excretion to bring us back into balance. The mammalian kidney actually uses both mechanisms to perform its job which is necessary for our survival on land. The adult kidney filters~150 l of isotonic fluid a day and reclaims most of it, leaving the waste produces to be excreted in about 1.5 l of urine. In addition, there are secretory processes for solutes such as organic anions and cations in the proximal tubule and secretory mechanisms to excrete the excess acid generated from metabolism in the distal nephron which aid in maintaining homeostasis.To accomplish the remarkable task of reclamation of the necessary solutes and water to maintain a constant composition of the extracellular fluid volume, the mammalian kidney has evolved into a highly specialized organ with thousands of units called nephrons. Each human kidney has approximately one million nephrons. Each nephron is a tube consisting of epithelial cells and is divided into 12 specialized segments as shown in Fig. 1. The epithelial cells allow for the vectorial transport of solutes. The proximal tubule is responsible for the bulk reclamation of solutes and water and for the secretion of organic cations and anions. Approximately two-thirds of the glomerular filtrate is reabsorbed by the proximal tubule in an isotonic fashion. Virtually all of the organic solutes, as well as the majority of bicarbonate, phosphate, and chloride, are reabsorbed in this segment. The proximal tubule is divided into S 1 , S 2 , and S 3 segments based on the rates of transport of some solutes and mor...

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Chloride Transport

Edwards

2012

Comprehensive Physiology

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Chloride transport along the nephron is one of the key actions of the kidney that regulates extracellular volume and blood pressure. To maintain steady state, the kidney needs to reabsorb the vast majority of the filtered load of chloride. This is accomplished by the integrated function of sequential chloride transport activities along the nephron. The detailed mechanisms of transport in each segment generate unique patterns of interactions between chloride and numerous other individual components that are transported by the kidney. Consequently, chloride transport is inextricably intertwined with that of sodium, potassium, protons, calcium, and water. These interactions not only allow for exquisitely precise regulation but also determine the particular patterns in which the system can fail in disease states. © 2012 American Physiological Society. Compr Physiol 2:1061‐1092, 2012.

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Maturation of rat proximal tubule chloride permeability

Cited by 19 publications

References 36 publications

Claudins 6, 9, and 13 are developmentally expressed renal tight junction proteins

Claudins 6, 9, and 13 are developmentally expressed renal tight junction proteins

Renal Tubular Development

Chloride Transport

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