ANTISENSE EVIDENCE FOR 2 FUNCTIONALLY ACTIVE FORMS OF NITRIC-OXIDE SYNTHASE IN BRAIN MICROVASCULAR ENDOTHELIUM

Other workers have identified two constitutive forms of NOS in endothe lial cells: endothelial or eNOS and neuronal or nNOS. The present stud y tests the functional significance of these NOS in brain surface arte rioles of mice. Antisense oligodeoxynucleotides (ODN) were injected in to the cerebral ventricles. Anti eNOS and anti nNOS were tested separa tely and in combination. Each antisense reduced the dilation produced by topical acetylcholine (ACh) or by tetrahydrobiopterin (THBP). These are endothelium dependent, NOS dependent dilators, with the THBP bein g a cofactor for NOS. The endothelium derived mediator actually causin g the dilation is EDRF((ACh)). When both antisenses were given togethe r there was an additive effect which approached 100% inhibition. Neith er sense nor mismatched (scrambled) ODN inhibited either ACh or THBP. Moreover, anti eNOS did not inhibit dilation by bradykinin (endotheliu m dependent but not NOS dependent) or by sodium nitroprusside (endothe lium independent). The data strongly support the conclusion that both eNOS and nNOS are functionally important in the endothelium of mouse p ial arterioles. Each isoform of NOS appears to contribute significantl y to the synthesis of basally released (THBP triggered) and agonist (A Ch) released EDRF(ACh). (C) 1996 Academic Press, Inc.