7-ethoxycoumarin deethylase activity as indicator of oxidative metabolism in rabbit eyes

Oxidative drug metabolism in intraocular tissues (choroid, cornea, iris-ciliary body and retina) plus conjunctiva and liver was determined in rabbits. 7-Ethoxycoumarin deethylase activity was found in all the intraocular tissues, but enzyme activities in these tissues were fairly low compared to activities in the conjunctiva and liver. Iris-ciliary body showed the highest enzyme activity and cornea showed the lowest. Relatively high activities were found in conjunctiva: 21 and 120 times as high as those in iris-ciliary body of young and adult rabbit eyes, respectively. The administration of phenobarbital or 3-methylcholanthrene (3-MC) to young rabbits caused marked induction of enzyme activity only in choroid tissues. Phenobarbital, but not 3-MC, also induced enzyme activities in conjunctiva and liver.