title: Bile salt-independent retinyl ester hydrolase in the rat lacrimal gland.
abstract: The lacrimal gland secretes retinol and synthesizes and stores retinyl esters. In this study, presence of retinyl ester hydrolase in rat lacrimal gland was investigated. A bile salt-independent retinyl ester hydrolase was identified in lacrimal gland homogenates and microsomes which were incubated in a tris-maleate buffer with retinyl palmitate as substrate. Retinol produced was measured by HPLC and activity expressed as pmoles retinol produced/mg protein/hr. In homogenates, the enzyme activity had a pH optimum at pH 6 and maximum specific activity of 57.7 pmoles/mg/hr. In microsomes, the activity was optimal at pH 7 and maximum specific activity was 1073 pmoles/mg/hr. In contrast, rat liver retinyl ester hydrolase had a pH optimum at pH 8 and a specific activity of 24.7 pmoles/mg/hr. These observations demonstrate that a complete cycle of retinyl ester metabolism is present in the lacrimal gland.
authors.affiliation: Department of Physiology, Medical College of Wisconsin, Milwaukee 53226.
authors.forename: D
authors.initials: D
authors.lastname: Lopez Bernal
authors.forename: J L
authors.initials: JL
authors.lastname: Ubels
mesh_terms: D000818:Animals; D001647:Bile Acids and Salts / Q000502:physiology; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D007765:Lacrimal Apparatus / Q000201:enzymology*; D008099:Liver / Q000201:enzymology; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D001647:Bile Acids and Salts; D002265:Carboxylic Ester Hydrolases; C022523:retinyl esterase