SPONTANEOUS CALCIUM-INDEPENDENT NITRIC-OXIDE SYNTHASE ACTIVITY IN PORCINE CILIARY PROCESSES

In the cornea, iris, retina, and ciliary precesses of porcine eyes the nitric oxide synthase (NOS) activity was assayed by measuring the tra nsformation of L-[U-C-14]-arginine into L-[U-C-14]-citrulline: (1) in the absence or presence of the calcium-chelator, ethylene glycol tetra acetic acid (EGTA), and (2) in the presence of EGTA and the false pre cursor of L-arginine, N-G-nitro-L-arginine methyl ester (L-NAME). In t he retina and the iris a high calcium-dependent NOS activity was prese nt, while in the cornea the activity was relatively low. In these thre e tissues no significant calcium-independent NOS activity was detected . In contrast, a marked calcium-independent NOS activity, but no calci um-dependent NOS activity, was found in the ciliary processes. The pre sence of a spontaneous calcium-independent NOS activity in the ciliary processes suggests that nitric oxide (NO) production is highly regula ted in this tissue. (C) 1996 Academic Press, Inc.