AMIDATIVE PEPTIDE PROCESSING AND VASCULAR FUNCTION

Substance P (SP), an amidated peptide present in many sensory nerves, is known to affect cardiovascular function, and exogenously supplied S P has been shown to activate nitric oxide synthase (NOS) in endothelia l cells. We now report that SP-Gly, the glycine-extended biosynthetic precursor of SP (which is enzymatically processed to the mature amidat ed SP), causes relaxation of rat aortic strips with an efficacy and po tency comparable to that of SP itself. Pretreatment of the aortic stri ps with 4-phenyl-3-butenoic acid (PBA), an irreversible amidating enzy me inactivator, results in marked inhibition of the vasodilation activ ity induced by SP-Gly but not of that induced by SP itself. Isolated e ndothelial cell basal NOS activity is also decreased by pretreatment w ith PBA, with no evidence of cell death or direct action of PBA on NOS activity. Both bifunctional and monofunctional forms of amidating enz ymes are present in endothelial cells, as evidenced by affinity chroma tography and Western blot analysis. These results provide evidence for a link between amidative peptide processing, NOS activation in endoth elial cells, and vasodilation and suggest that a product of amidative processing provides intrinsic basal activation of NOS in endothelial c ells.