Steroid metabolism in ocular tissues of the rabbit.
The metabolism of cortisol and other steroids was studied in normal untreated rabbit iris-ciliary body and cornea as part of an investigation into the mechanism of glucocorticoid-induced glaucoma. Cortisol is readily converted to the inactive metabolite cortisone by these eye tissues indicating the presence of an 11beta-oxidoreductase system. This reaction is reversible with cortisone being converted to cortisol in the presence of appropriate cofactor. However, due to the absence of a (or as yet undetectable) cortisol-A-ring-reductase system (rate-limiting reaction) the steroid is not irreversibly metabolized to biologically inactive compounds. The 11beta-oxidoreductase system readily converts other C21-11beta-hydroxysteroids, such as corticosterone, to its appropriate C21-11-ketosteroid (11-dehydrocorticosterone). Some C21-steroids lacking the 11-hydroxyl group (11-deoxycortisol, 11-deoxycorticosterone) remain virtually unmetabolized (exception to this was found with progesterone). Evidence of a C21-steroid A-ring reductase system was found only when cortisone and progesterone were used as substrates. However, testosterone a C19 steroid was converted to clearly identifiable A-ring reduced and 17beta-and 3alpha(beta)-oxidoreduced metabolites, thus indicating the presence of testosterone A-ring reductase, 17beta-and 3alpha(beta)-oxidoreductase systems in the eye tissues studied. The presence of a steroid 5alpha(beta)-reductase for some steroids but not for cortisol indicates a distinct substrate specificity for this enzyme system in the eye tissues.
D000735:Androstenedione / Q000031:analogs & derivatives / Q000378:metabolism; D000818:Animals; D002924:Ciliary Body / Q000378:metabolism; D003067:Coenzymes / Q000378:metabolism; D003345:Corticosterone / Q000378:metabolism; D003348:Cortisone / Q000378:metabolism; D003350:Cortodoxone / Q000378:metabolism; D003900:Desoxycorticosterone / Q000378:metabolism; D005123:Eye / Q000201:enzymology / Q000378:metabolism*; D005938:Glucocorticoids / Q000378:metabolism*; D006854:Hydrocortisone / Q000378:metabolism; D007498:Iris / Q000378:metabolism; D008297:Male; D011374:Progesterone / Q000378:metabolism; D011817:Rabbits; D013739:Testosterone / Q000378:metabolism; D013760:Tetrahydrocortisol / Q000378:metabolism
D003067:Coenzymes; D005938:Glucocorticoids; D013739:Testosterone; D000735:Androstenedione; D003900:Desoxycorticosterone; D011374:Progesterone; D013760:Tetrahydrocortisol; D003348:Cortisone; D003345:Corticosterone; D003350:Cortodoxone; D006854:Hydrocortisone