THE CONTRIBUTIONS OF GLYCOSAMINOGLYCANS, COLLAGEN AND OTHER INTERSTITIAL COMPONENTS TO THE HYDRAULIC RESISTIVITY OF PORCINE AORTIC-WALL

A pressure-driven flux of water occurs across the arterial wall in viv o. We have investigated the role of several interstitial components in determining the resistance of the wall to this flow. Pieces of porcin e thoracic aorta were modified by thermal denaturation, enzymatic dige stion or disruptive chemical treatments. The effect of these procedure s on the wall content of glycosaminoglycans, collagen and elastin was determined by biochemical assay of uronic acid and hydroxyproline, Eff ects on hydraulic conductivity were measured by using a flow cell in w hich tissue was free to deform under applied pressure. Untreated tissu e showed considerable variation in uronic acid content but conductivit ies were substantially less variable and averaged 0.75 x 10(-12) cm(4) /dyne.s. In tissue autoclaved for < 1 h, resistivity increased, possib ly because interstitial components had been denatured but not removed from the wall. After longer periods, resistivity decreased by a factor of one hundred. More specific treatments showed that resistivity decr eased by up to a factor of ten when glycosaminoglycans were removed an d by a similar factor when collagen was removed, Tissue in which both were removed showed a hundred-fold decrease in resistivity. As with ti ssue subjected to prolonged autoclaving, the resistivity was still an order of magnitude higher than that of alkali- or acid-extracted elast in despite an apparently similar composition, suggesting the existence of a non-assayed component with important properties. The resistivity of the samples was decreased further by treatment with chymotrypsin, consistent with this component being microfibrillar protein.