HUMAN RETINA EXPRESSES BOTH CONSTITUTIVE AND INDUCIBLE ISOFORMS OF NITRIC-OXIDE SYNTHASE MESSENGER-RNA

The present study provided evidence for the presence of two forms of n itric oxide synthase(NOS) gene in the human retina. Expression of reti nal constitutive type(rbNOS) and inducible type(riNOS) of NOS was dete cted in human retinal poly A(+)RNA by reverse transcriptase polymerase chain reaction(RT-PCR) method. The deduced amino acid sequence of the human retinal rbNOS showed more than 99% homology with human brain bN OS and that of riNOS was identical to the chondrocytes inducible iNOS with the exception for one amino acid. These differences in amino acid sequences of rbNOS and riNOS,with their counterparts in human brain a nd human chondrocytes sequences,were only in the non-cofactor binding sites. Northern blot analysis of the human retinal poly Af RNA and tot al RNA, using the PCR-amplified riNOS probe revealed the existence of riNOS message with the appearance of the band with the expected size o f 4.4kb, while the message for rbNOS was not detectable. This was the first report of the deduced nucleotide sequence identification of two NOS genes from a human tissue, while there had been earlier reports fr om culture cells. (C) 1994 Academic Press, Inc.