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Recombinant enkephalinase effectively inhibits substance P-induced miosis in the rabbit eye cup model
J A Anderson1, E Hernandez, E Duzman
1Ophthalmology Research Laboratory, Sharp Cabrillo Hospital, San Diego, CA.
Abstract:
Enkephalinase (EC 3.4.24.11) is a naturally occurring, membrane-bound peptidase that degrades substance P in vivo and in vitro. Addition of this neutral endopeptidase to a rabbit eye cup model partially inhibits substance P-induced contraction of the iris sphincter muscle. Inactivation of substance P is reversed by thiorphan, a specific inhibitor of enkephalinase. These results show that enkephalinase degradation of substance P produces metabolites that are physiologically inactive in iris contraction. We also observed that atropine acts synergistically with enkephalinase to completely abolish substance P-induced iris contraction suggesting that the action of substance P on the iris contains an acetylcholine-stimulatory effect which is not lost by enkephalinase treatment.