Effects of sugars and amino acids on sodium and potassium influx in rabbit ileum

Dose-dependence of endoneurial fluid sodium and chloride accumulation in galactose intoxication

Endoneurial edema in galactose neuropathy was studied in a colony of Sprague-Dawley rats fed diets containing 0%, 10%, 20% or 40% D-galactose for approx. 200 days. Endoneurial fluid was analyzed by X-ray microanalysis for electrolyte concentration, by microgravimetry of whole nerve segments for water content, by measurement of endoneurial fluid pressure and by morphometry in transverse sections of nerve. Galactose intoxication resulted in dose-dependent increases in endoneurial fluid sodium and chloride that were directly associated with increases in nerve water content and endoneurial fluid pressure. The presence of edema and its dose-dependence was also confirmed by morphometric analysis of sciatic nerves at the light microscopic level. The data demonstrate that electrolyte-induced osmotic imbalances in endoneurial fluid are dependent on the amount of galactose ingested and suggest that the dose-related accumulation of sodium and chloride in endoneurial fluid contributes substantially to the pathogenesis of galactose neuropathy.

Endoneurial sodium accumulation in galactosemic rat nerves

Microdrop samples of endoneurial fluid and serum from galactosemic rats were analyzed with energy dispersive spectrometry (EDS). The sodium concentration of endoneurial fluid from galactose-fed rats (295 meq/liter) was nearly twice that of age-matched controls (152 meq/liter) and indicates that sodium is present in an osmotically significant concentration that is capable of causing the edema and increased endoneurial fluid pressure (EFP) associated with galactose neuropathy. It is suggested that accumulation of endoneurial sodium is linked to the movement of sugar into the endoneurium.

Edema and increased endoneurial sodium in galactose neuropathy. Reversal with an aldose reductase inhibitor

Galactose neuropathy was produced in rats by feeding a diet containing 30% D-galactose. After 12 weeks of galactose ingestion, all rats developed bilateral cataracts, polydypsia and polyuria. These galactose-intoxicated animals were divided into two groups that both continued with the galactose diet: animals that were treated with the aldose reductase inhibitor, ICI 128,436, for 4-6 weeks, and a control group of animals that received just excipient. At the end of the study, endoneurial fluid pressures, nerve water contents and endoneurial fluid electrolyte concentrations were determined from sciatic nerves of treated and untreated animals. The extent of neuropathy in each animal was evaluated by light microscopy. Treatment of galactose-intoxicated rats with ICI 128,436 restored to normal levels the elevated endoneurial sodium concentration, increased water content and interstitial fluid pressure characteristic of galactose neuropathy. These results, obtained with an agent that blocks the sorbitol pathway, associate elevated sodium with an osmotic force contributing to edema and increased endoneurial fluid pressure in galactose neuropathy and suggest that endoneurial sodium levels are linked to blood-sugar concentration.