Permeability and Respiration Effects of Thyroidal Hormones on the Isolated Bladder of the Toad Bufo Bufo

Matty, A. J.; Green, K.

doi:10.1677/joe.0.0250411

Cited by 27 publications

(20 citation statements)

References 14 publications

(24 reference statements)

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Section: Discussionmentioning

confidence: 82%

“…Other studies suggested that thyroid hormone may be involved in the regulation of the permeability of the paracellular pathway (38)(39)(40). Thyroid hormone has been shown to decrease the resistance of toad bladders (40).…”

Section: Discussionmentioning

confidence: 99%

“…Thyroid hormone has been shown to decrease the resistance of toad bladders (40). In addition, the bath to lumen flux of 36 C and 32 P increased with thyroid hormone administration, consistent with a decrease in the paracellular permeability to these anions (39,40). However, passive phosphate and calcium transport across the small intestine was less in rats that received thyroid hormone for 7 d than in control rats, consistent with a decrease in paracellular movement of these ions with thyroid hormone treatment (38).…”

Section: Discussionmentioning

confidence: 99%

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Developmental Changes in Proximal Tubule Tight Junction Proteins

et al. 2005

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We demonstrated previously that neonatal proximal tubules have a lower passive paracellular permeability to chloride ions and higher resistance than that of adult proximal tubules. In addition, administration of thyroid hormone to neonates, before the normal maturational increase in serum thyroid hormone levels, prematurely accelerates the developmental increase in chloride permeability to adult levels. To test the hypothesis that there is a maturational change in tight junction proteins and that thyroid hormone mediates these changes, we examined the two known tight junction proteins present in proximal tubules, occludin and claudin 2. Using immunoblot and immunohistochemistry, we demonstrated that claudin 2 has a 4-fold greater abundance in neonatal proximal tubules than in adult tubules. Occludin, however, has a 4-fold greater expression in adult tubules than in neonatal tubules. Administration of thyroid hormone to neonates did not affect claudin 2 expression, occludin expression, or the transepithelial resistance in rat proximal tubule cells in vitro. In conclusion, there are postnatal maturational changes in tight junction proteins. The factors that cause these maturational changes are unknown but unlikely to be due solely to the maturational increase in thyroid hormone.The proximal tubule receives an ultrafiltrate from the glomerulus and reabsorbs two thirds of the ultrafiltrate in a nearly iso-osmotic manner. In addition to active transcellular fluid transport, the proximal tubule reabsorbs solutes via passive diffusion across the paracellular pathway. The early proximal tubule reabsorbs glucose and amino acids and preferentially reabsorbs bicarbonate over chloride ions (1,2), which leaves the luminal fluid delivered to the late proximal tubule with a higher chloride concentration and lower bicarbonate concentration than that in the peritubular plasma (1,2). Passive solute transport is dependent on the gradients that develop between lumen and peritubular capillary and permeability properties of the paracellular pathway.Approximately two thirds of the filtered chloride is reabsorbed by the adult proximal tubule (1,3 active and transcellular and half is passive and paracellular (3-5). Active NaCl transport is mediated by the parallel operation of the Na+/H+ exchanger and a Cl−/base exchanger (3,4). Passive Cl absorption is mediated by diffusion of chloride ions down its concentration gradient generated in the early proximal tubule (6,7). Thus, the permeability properties of the paracellular pathway can affect a significant amount of proximal tubule NaCl transport.Furthermore, the permeability properties of the paracellular pathway serve as a barrier to prevent the back diffusion of glucose, amino acids, phosphate, bicarbonate, and other solutes that are in higher concentration in the peritubular fluid than in the lumen of the late proximal tubule. In previous in vitro rabbit microperfusion studies, our laboratory demonstrated that unlike the adult segment, the neonatal proximal tubule was impermeab...

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Section: Discussionmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Developmental Changes in Proximal Tubule Tight Junction Proteins

et al. 2005

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“…Thyroid hormone was shown 35 years ago to affect passive paracellular anion permeability in isolated toad bladders (20,21). After thyroxine treatment, there was an increase in shortcircuit current but no change in electrical potential, consistent with a concomitant increase in paracellular permeability.…”

Section: Discussionmentioning

confidence: 88%

Maturation of proximal straight tubule NaCl transport: role of thyroid hormone

Shah¹,

Quigley²,

Baum

2000

American Journal of Physiology-Renal Physiology

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We have recently demonstrated that the rates of both active and passive proximal straight tubule (PST) NaCl transport in neonatal rabbits were less than in adults. In this segment NaCl entry across the apical membrane is via parallel Na + /H + and Cl − /OH − exchangers, which increases in activity with maturation. The present in vitro microperfusion study examined whether thyroid hormone plays a role in the maturational increase in PST NaCl transport. Neonatal and adult PST were perfused with a high-chloride-low bicarbonate solution without organic solutes, simulating late proximal tubule fluid. Thyroid hormone-treated neonates had a higher rate of PST total and passive NaCl transport. In 8-wk-old animals that were hypothyroid since birth, the maturational increase in total and passive NaCl transport was prevented. Thyroid treatment for 4 days in hypothyroid 8-wk-old rabbits increased the rate of both total and passive NaCl transport. The maturational increases in both Na + /H + and Cl − /OH − exchange activities were blunted in 8-wk-old hypothyroid animals and increased to control levels with thyroid treatment. This study demonstrates that thyroid hormone is a factor responsible for the maturational increase in both active and passive PST NaCl transport.Keywords sodium/hydrogen antiporter; chloride/base exchanger; kidney development; passive transportThe Proximal Tubule Reabsorbs ~60% of the filtered NaCl. The preferential reabsorption of organic solutes and bicarbonate by the early proximal tubule leaves the luminal fluid with a higher chloride and lower bicarbonate concentration than the peritubular plasma (19,24). In the proximal tubule approximately one-half of NaCl transport is passive and paracellular (4,25). The parallel operation of the apical membrane Na + /H + antiporter and Cl − /base exchangers mediate NaCl entry into the proximal tubule cell (1,18,25 We have recently examined the postnatal developmental changes in proximal straight tubule (PST) NaCl transport (25). In rabbit PST perfused with a high chloride-low bicarbonate solution simulating late proximal tubular fluid and bathed in a serum-like albumin solution, the rate of volume absorption, a reflection of both active and passive NaCl transport, was over twofold higher in the adult than neonatal segment (25). NaCl transport was inhibited by 50% by bath ouabain in adult tubules and totally inhibited in the neonatal segment. Thus the rates of active and passive NaCl transport were higher in the adult tubule than were those in the neonate (25).In the rabbit PST there was a fivefold increase in the Na + /H + antiporter activity during postnatal development (25). Cl − /base exchange in neonatal and adult PST was not affected by cyanide and acetazolamide, CO 2 and bicarbonate, or the addition of formate, consistent with Cl − /OH − exchange (18, 25). There was a sixfold maturational increase in apical membrane PST Cl − /OH − exchange activity (25).The factors that produce the profound postnatal changes in active and passive proximal tubular t...

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“…These values are of the same order of magnitude as those found for other anuran amphibians [Sawyer and Schisgall, 1956;Bentley, 1958;Bourguet andM a etz. 1961: M atty andG reen. 1963].…”

Section: Bladdermentioning

confidence: 99%

Neurohypophysial Hormones and Homeostasis in the Crab-Eating Frog, <i>Rana cancrivor</i><i>a</i>

Dicker¹,

Elliott²

1973

Horm Res

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Mechanisms of homeostasis in a euryhaline amphibian, Rana cancrivora, the crab-eating frog, are reviewed and discus-sed. While plasma osmolality of R. cancrivora is always greater thanthe bathing fluid (from 0 to 800 mOsmole), urine is always dilutewith reference to plasma. Homeostasis is maintained by the factthat the skin, though permeable to water, is insensitive to the actionof neurohypophysial hormones, the potential differences, short circuit current and net influx of Na+ across it being smaller than inother anuran amphibians. The hypertonicity of the plasma when the frog is in saline solutions is achieved by an increase of plasma NaCl and urea concentration. The mechanism by which plasma urea concentration increases from 40 mM when the frog is in fresh water to 400 mM when in brackish water can be explained by an initial diffusion of urea from the bladder, followed by an enhanced activity of the enzymes of the ornithine-urea cycle. Rapid diffusion of urea into muscles protects the latter against damage due to hypertonicity of the plasma and extracellular fluid. Neurohypophysial hormones appear to act mainly on the bladder where they appear to increase the permeability to urea. The gastrointestinal tract does not play a major role in the mechanism of adaptation to hypertonic solutions. The significance of the different mechanisms used by R. cancrivora to maintain homeostasis are discussed in relation to similar problems in other anuran amphibians.

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Permeability and Respiration Effects of Thyroidal Hormones on the Isolated Bladder of the Toad Bufo Bufo

Cited by 27 publications

References 14 publications

Developmental Changes in Proximal Tubule Tight Junction Proteins

Developmental Changes in Proximal Tubule Tight Junction Proteins

Maturation of proximal straight tubule NaCl transport: role of thyroid hormone

Neurohypophysial Hormones and Homeostasis in the Crab-Eating Frog, <i>Rana cancrivor</i><i>a</i>

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