AGE-RELATED-CHANGES IN RAT INTERSTITIAL MATRIX HYDRATION AND SERUM-PROTEINS

Measurements of effects of age-related changes on loose connective tis sue protein concentrations and water are lacking. Tissue hydration is an important determinant of tissue protein diffusion coefficients and hydraulic conductivity. Sprague-Dawley rats (ages 11, 30, 57, and 89 w k) were anesthetized. Blood and mesenteric tissue samples were taken. Tissue water content was determined by microgravimetric technique. Pro tein content was determined by electrophoresis. Tissue hydration decre ased 18% between 11 and 89 wk with one-half the fall occurring between 57 and 89 wk. Tissue albumin concentration decreased 37% between 11 a nd 89 wk. Serum albumin increased 22% between 11 and 30 wk and then de creased by 37% to 1.4 g/dl in 89-wk rats. Serum total protein concentr ation increased by 13% between 11 and 89 wk, whereas tissue total prot ein concentration decreased 30% with age to 1.9 g/dl at 89 wk. The res ults suggest that age-related tissue dehydration is due, in part, to a shift in the colloid osmotic pressure components of Starling equilibr ium favoring fluid reabsorption.