THE DISTRIBUTION OF WATER IN ARTERIAL ELASTIN - EFFECTS OF MECHANICAL-STRESS, OSMOTIC-PRESSURE, AND TEMPERATURE

Using gravimetric and radiotracer techniques, we investigated the effe cts of mechanical stress, osmotic pressure, and temperature on the vol umes of the intra- and extrafibrillar water spaces in arterial elastin . We also investigated the effects of temperature on water flow throug h elastin membranes and on dynamic mechanical properties of elastin ri ngs. Compression by mechanical or osmotic loading reduced the hydratio n of the elastin in an identical manner Two distinct stages were evide nt; at low loads there was extensive water removal from the extrafibri llar space while high loads were required to remove water from the int rafibrillar space. Conversely, dehydration caused by mechanical extens ion of the matrix was associated with a much smaller loss from the ext rafibrillar compartment and a large fractional decrease in the intrafi brillar space. Contraction of the matrix as a result of increased temp erature had similar effects on hydration to those produced by extensio n. Water flux across elastin membranes, corrected for changes in visco sity, and specific hydraulic conductivity both increased as a result o f temperature-induced contraction. This effect was attributed to incre ases in both the fractional volume of the extrafibrillar space and the fiber radius. The elastic modulus deceased with increasing temperatur e but there was an increase in viscoelasticity. Previous studies have determined that viscoelasticity depends on the rate of redistribution of intrafibrillar water, so this finding provides additional evidence that heating affects primarily the volume of the intrafibrillar space. (C) 1995 John Wiley & Sons, Inc.