title: Effect of brimonidine on rabbit trabecular meshwork hyaluronidase activity.
abstract: OBJECTIVE
  To study the presence of hyaluronidase activity in the rabbit trabecular meshwork and its regulation by brimonidine.
  
  
  METHODS
  A spectrophotometric assay that consists of the assessment of N-acetylhexosamine groups released from hyaluronic acid was used to examine hyaluronidase activity. Cyclic adenosine monophosphate (cAMP) levels were assessed by radioimmunoassay.
  
  
  RESULTS
  Hyaluronidase activity was detected in the rabbit trabecular meshwork. Its optimal activity was in the acid range of pH 3.8. Brimonidine significantly increased trabecular hyaluronidase-specific activity and decreased cAMP accumulation. Yohimbine significantly inhibited the effect of brimonidine on both hyaluronidase activity and cAMP accumulation.
  
  
  CONCLUSIONS
  The finding of endogenous hyaluronidase activity in rabbit trabecular meshwork supports the hypothesis that this tissue can metabolize its own glycosaminoglycan (GAG) products. The present results suggest, however, that the hypotensive effect of brimonidine could be mediated, at least in part, by its ability to increase GAG catabolism, probably through a cAMP-independent mechanism.
authors.affiliation: Departamento de Bioquímica Humana, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
authors.forename: J
authors.initials: J
authors.lastname: Benozzi
authors.forename: C O
authors.initials: CO
authors.lastname: Jaliffa
authors.forename: F
authors.initials: F
authors.lastname: Firpo Lacoste
authors.forename: D W
authors.initials: DW
authors.lastname: Llomovatte
authors.forename: M I
authors.initials: MI
authors.lastname: Keller Sarmiento
authors.forename: R E
authors.initials: RE
authors.lastname: Rosenstein
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D000068438:Brimonidine Tartrate; D000242:Cyclic AMP / Q000378:metabolism; D006821:Hyaluronoglucosaminidase / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008297:Male; D011810:Quinoxalines / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011817:Rabbits; D011863:Radioimmunoassay; D014129:Trabecular Meshwork / Q000187:drug effects* / Q000201:enzymology; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D011810:Quinoxalines; D015016:Yohimbine; D000068438:Brimonidine Tartrate; D000242:Cyclic AMP; D006821:Hyaluronoglucosaminidase