Hyaluronan Content in Human Inner Ear Fluids

Abstract

Histochemical analyses of the luminal contents of the endolymphatic sac in numerous mammalian species have indicated a presence of acid mucopolysaccharides or proteoglycans. In the present study, one of these substances, hyaluronan (hyaluronic acid; HA), in endolymphatic sac endolymph and vestibular perilymph in humans, was biochemically determined with a highly specific radioassay. A considerable variation in HA concentration was noted between the individual ES endolymph samples, with a mean value of 2.50 μg/g (range 0.00-10.86). In perilymph the HA concentrations were less variable and the mean concentration was 0.91 μg/g (range 0.56-1.51). The difference between endolymph and perilymph HA concentration was not statistically significant (p > 0.05). The ability of HA to interact with proteoglycans, thereby forming giant hydrophilic molecules, could be important for ES function. These molecules may create a swelling pressure which is resistant to compressive forces that under conditions of increased intracranial hydrostatic pressure otherwise could cause ES collapse and impaired function.

Key Words:

• endolymphatic sac
• perilymph