CONTENT AND FORMATION OF PROSTAGLANDINS AND DISTRIBUTION OF PROSTAGLANDIN-RELATED ENZYME-ACTIVITIES IN THE RAT OCULAR SYSTEM

Abstract

The steady-state levels of prostaglandin D2, E2 and F2.alpha. in the rat eye were 0.5, 0.1 and 1.0 ng/g, respectively, which increased differently among the prostaglandins after a 40-min incubation of the homogenate at 37% C (to 23, 12 and 14 ng/g, respectively). When the eye was dissected into anterior uveal, scleral, and retinal complexes, prostaglandin D2 was formed in the highest degree in all the complexes, whereas prostaglandin E2 and F2.alpha. formation was specific to given ocular regions. Three prostaglandin synthetase activities with similiar Km values (20-40 .mu.M) were found in the 10 000 .times. g supernatant of these tissues, i.e., GSH-independent and soluble D, GSH-dependent and membrane-bound E, and soluble F synthetase activities. These enzyme activities correlated well with the prostaglandin formation in each tissue. D synthetase activity being highest in all tissues (11-25 nmol/min per g). Three types of prostaglandin-catabolizing enzyme activities were detected in the 100,000 .times. g supernatant of the tissues, i.e., type II 15-hydroxy dehydrogenase (Km = 10-30 .mu.M), 9-keto (500 .mu.M) and 11-keto reductase (2.5 mM). The activity of the dehydrogenase was low even in the retina, the tissue with the highest levels (0.51, 0.35 and 0.15 nmol/min per g for prostaglandin E2, F2.alpha. and D2, respectively).