PARTIAL BIOCHEMICAL-CHARACTERIZATION OF NITRIC-OXIDE SYNTHASE IN THE CAUDAL SPINAL-CORD OF THE TELEOST OREOCHROMIS-NILOTICUS

The present study demonstrates that a NADPH/Ca2+-dependent nitric oxid e synthase (NOS) activity is present in the soluble and in the particu late fractions of fish caudal spinal cord homogenates, both activities being inhibited by calmodulin inhibitors (W7 and/or TFP) and by the N OS inhibitor L-NAME. Moreover, Western blot analysis using either anti -NOS I or anti-NOS ill antibodies shows that the soluble enzyme corres ponds to the brain NOS (NOS-I) of mammals, whereas the particulate one is likely attributable to NOS I and/or NOS III (ecNOS) enzymes. To co nfirm the nitric oxide (NO) production by the caudal spinal cord homog enates, the NO-mediated conversion of oxyhemoglobin to methemoglobin w as monitored spectroscopically. The present results are consistent wit h a constitutive, Ca2+-calmodulin-dependent, NO production by the caud al neurosecretory system. (C) 1998 Elsevier Science Ireland Ltd. All r ights reserved.