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Jorge Benozzi, Carolina O. Jaliffa, Francisco Firpo Lacoste, Diego Weinberg Llomovatte, María I. Keller Sarmiento, Ruth E. Rosenstein; Effect of Brimonidine on Rabbit Trabecular Meshwork Hyaluronidase Activity. Invest. Ophthalmol. Vis. Sci. 2000;41(8):2268-2272.
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purpose. 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
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.
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