Sodium and Chloride Spaces and Water Content of Tendon in Normal and Depleted Rats

¹ From the Department of Physiology, Washington University School of Medicine, St. Louis, Missouri

In normal rat tail tendon where evaporation is prevented, sodium space is significantly lower than water (P < 0.001), while chloride space is not significantly different from water (P = 0.2). On acute sodium and chloride depletion by intraperitoneal dialysis with 4.5% mannitol, the observed changes in sodium or chloride space/water are not significant (P > 0.05). Rat tail tendon water closely resembles plasma ultrafiltrate with respect to chloride concentration, but its sodium concentration is less than that of an ultrafiltrate.