Spatial distribution of protein in interstitial matrix of rat mesenteric tissue.

Interstitial matrix protein has been measured by collecting fluid from implanted capsules and wicks. If the interstitial matrix is well mixed, then these measurements provide an accurate indication of perivascular protein concentration. However, there is increasing evidence suggesting that interstitial protein distribution is nonuniform. To test this hypothesis, a combined light-scattering and protein absorbance image of mesenteric tissue in a pentobarbital-anesthetized rat was obtained by using an ultraviolet-sensitive television camera to perform videomicrospectrophotometry. In avascular tissue regions protein was organized into periodic nonuniform ridges and valleys. On a smaller scale, the protein along a ridge was organized into clusters. Similar clusters were seen along the wall of small tortuous microvessels and were accompanied by radial gradients in protein distribution. High protein concentration tunnels were occasionally seen extending from a microvessel into the interstitial matrix. A two-way analysis of variance shows that macromolecular spatial distribution is nonuniform (P less than 0.001). Thus the hypothesis that the extracellular matrix is well mixed fails for macromolecules in rat mesenteric loose connective tissue.