Distribution and Induction of Alkoxyresorufin O-dealkylases and Gamma-Glutamyl Transpeptidase in Porcine Ciliary Epithelium

Abstract

Nongpigmented epithelial (NPE) cells and pigmented epithelial (PE) cells were separated from porcine ciliary body by a simple surgical procedure. Using primary cultures of separated cells, basal and induced activities of 7-ethoxy resorufin (ER) O-dealkylase, 7-pentoxy resorufin (PR) O-dealkylase, and gamma-glutamyl transpeptidase (GGTP) were determined. These enzymatic activities were primarily associated with NPE cells; PE cells showed little or no activity. Treatment of NPE cells with phenobarbital for 48 hours resulted in about 5-fold increase in PR O-dealkylase activity but not ER-Odealkylase activity. Conversely, 3-methylcholanthrene treatment increased ER O-dealkylase activity 5-6 times over the basal level but had little or nor effect on PR O-dealkylase activity. The enhancement of enzymatic activities by inducers was completely inhibited by cyclohexamide. NPE cells exhibited higher GGTP activity than PE cells. Both phenobarbital and 3-methylcholanthrene augmented the GGTP activity of NPE cells but not of PE cells. The physiological significance of the regional differences in enzyme distribution was discussed.