CHANGES IN RAT MESENTERY INTERSTITIAL MATRIX DUE TO SUPERFUSATE

Animal preparations for microscopy often require a superfusate solution to cover surgically exposed tissue. There are few, if any, data concerning the effects of this solution on extravascular protein concentration and hydration. The effect of superfusion on mesenteric tissue in anesthetized male Sprague-Dawley rats was studied. Tissue samples were taken from nonsuperfused and superfused tissue and analyzed for hydration, albumin, and transferrin content. The mesenteric tissue interstitial matrix was rapidly altered by normal saline superfusate. After superfusion, there was a decrease (P < 0.01) in tissue albumin concentration from 1.17 +/- 0.27 to 0.10 +/- 0.08 g/dl (n = 9). Tissue hydration increased from 4.98 +/- 0.8 mug water/mug dry wt in controls to 7.38 +/- 1.2 mug water/mug dry wt after superfusion. When a range of superfusate albumin concentrations was used (0, 1, 2, and 3 g/dl), tissue albumin concentration changed 0.59 +/- 0.09 g/dl for each gram per deciliter change in superfusate concentration (P < 0.0001). The large changes in interstitial matrix protein content and hydration suggest that superfusate solution effects need to be considered in microvascular protein transport experiments.