Distribution spaces for hyaluronan and albumin in rat tail tendons

A low concentration of hyaluronan (HA) in lymph compared with tissue sugges ts a large bound fraction. To investigate the distribution and mobility of HA and serum albumin (Alb), we eluted the rat tail tendon with a series of 15 successive centrifugations, each preceded by the addition of 0.15 M NaCl (15% of initial wet wt). The eluate concentration fell exponentially versu s the accumulated eluate, allowing estimation of the maximal elutable amoun t (E-HA and E-AIb). Alb elution was practically complete from a space of ap proximate to 28% of wet wt at all centrifugation rates. Twenty percent of H A was elutable at 500 rpm, apparently from the same space as Alb, increasin g to 40% at >4,000 rpm. This pattern was not significantly influenced by us ing 2 M NaCl or by the addition of plasma or metabolic inhibitors. Without prehydration and centrifugation at high revolutions per minute, both Alb an d HA concentrations fell rapidly toward zero, presumably in part reflecting mobilization of HA- and Alb-free fluid from the collagen intrafibrillar sp ace (3). We conclude that with prehydration the fibrils swell, increasing t he intramolecular spaces to become "penetrable" to HA and allowing removal of HA-containing fluid when the fibrils are compressed by the next centrifu gation at high revolutions per minute, increasing E-HA from 23 to 45%. Chem ical binding presumably explains the unelutable 55% of tendon HA. Intrafibr illar HA may act to stabilize the fibrillar volume.