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Spontaneous Calcium-Independent Nitric Oxide Synthase Activity in Porcine Ciliary Processes

Elsevier Inc.
Publication Date
DOI: 10.1006/bbrc.1996.0822


Abstract In the cornea, iris, retina, and ciliary processes of porcine eyes the nitric oxide synthase (NOS) activity was assayed by measuring the transformation of L-[U-14C]-arginine into L-[U-14C]-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 precursor of L-arginine, NG-nitro-L-arginine methyl ester (L-NAME). In the retina and the iris a high calcium-dependent NOS activity was present, while in the cornea the activity was relatively low. In these three tissues no significant calcium-independent NOS activity was detected. In contrast, a marked calcium-independent NOS activity, but no calcium-dependent NOS activity, was found in the ciliary processes. The presence of a spontaneous calcium-independent NOS activity in the ciliary processes suggests that nitric oxide (NO) production is highly regulated in this tissue.

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