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At least 91 records · Page 5Linked to original sources
PubMed1994

Studies of water movement across the gut using oral rehydration solutions in a rat perfusion model.

AIM: To measure water influx and efflux, as well as net water, sodium and potassium absorption from a range of oral rehydration solutions (ORS) in which the glucose content had been partially replaced with the amino acid leucine or with food supplements. METHODS: A series of in vivo steady-state perfusion studies in normal rat intestine. The oral rehydration solutions contained 60 or 90 mmol/L of sodium. The reference solution used was the World Health Organization (WHO) formula. RESULTS: There was a significant negative correlation between the oral rehydration solution osmolality and net water absorption (r = -0.722, P < 0.05). The highest net water absorption occurred using comminuted chicken supplemented oral rehydration solution containing 60 mmol/L sodium (P < 0.001). This oral rehydration solution also showed a significant increase in the rate of influx of water (P < 0.05) in comparison with the WHO formula containing 60 mmol/L sodium. CONCLUSION: This work provides further evidence that food-based oral rehydration solutions, including non-vegetable sources, may have a useful role to play in the management of patients with acute diarrhoea.

Amino Acids↗
PubMed1995

Correlation between chloride flux via the mitochondria-rich cells and transepithelial water movement in isolated frog skin (Rana esculenta).

The coupling between net transepithelial Cl- influx and net water flow was investigated. Experiments were performed on isolated frog skin bathed in isotonic Cl- Ringer's solution in the presence of the Na+ channel blocking agent amiloride in the mucosal solution. The skins were voltage-clamped at -80 or -100 mV (with the serosal solution as reference). Under these conditions the current across the skin is carried by an influx of Cl-. In the absence of antidiuretic hormone the correlation between current and net water flow was low, but in the presence of the antidiuretic hormone, arginine vasotocin, there was a highly significant correlation between current and net water flow. The data presented here indicate that under steady state conditions about 70 molecules of water follow each Cl- ion across the skin. If the water influx is driven by electroosmosis one would expect that a change in current should result in an immediate change in the water flow. There was, however, a considerable time delay between the change in current and water flow. This indicates that the observed coupling between Cl- flux and water flow is caused by current-induced local osmosis and not electroosmosis.

Amiloride↗
PubMed2003

Regulation of water movement across vertebrate renal tubules.

Kidneys play an essential role in fluid-ion balance, but the mechanisms of renal handling of water vary depending on structural organization of kidneys and the environment. Fishes and amphibians in a hypoosmotic environment excrete excess water by forming dilute urine, whereas terrestrial tetrapods require water conservation by the kidney for survival. Diluting segments operated by a luminal Na(+)-K(+)-2Cl(-) cotransporter coupled with a basolateral Na(+)-K(+) pump are essential in forming dilute urine. In birds and mammals, the diluting segment that has the same transport characteristics now serves, with the development of additional architectural organization, for countercurrent urine concentration and water conservation. Recently, a number of aquaporin (AQP) water channels have been identified in various transporting epithelia. AQPs conserve the NPA (asparagine-proline-alanine) motif, forming pores selective to water. Although all vertebrate kidneys presumably possess AQP water channels, AQP homologues have been cloned only from amphibian, avian and mammalian renal systems. Studies on expression sites, function and regulation of AQPs will provide important insight into cellular and molecular mechanisms of epithelial water transport and its control by humoral, neural and hemodynamic mechanisms.

Animals↗
PubMed1991

Measurement of water movement in the rabbit eye in vivo using H2(17)O.

Topically applied (eyedrop) H2(17)O (10% enrichment) was used in magnetic resonance studies to quantify intraocular water dispersion in vivo. The rate of H2(17)O removed from the aqueous chamber is in the order of 0.1 ml/min/ml of tissue. Similar results are obtained with either proton imaging or 17O spectroscopy. Parallel experiments of direct injection of H2(17)O into the aqueous chamber supported the topical data. Proton MR imaging of H2(17)O dissipation from the aqueous chamber with clinical imagers, coupled with eyedrop application, suggests clinical possibilities.

Animals↗