ACCUMULATION OF ENDOGENOUS INHIBITORS FOR NITRIC-OXIDE SYNTHESIS AND DECREASED CONTENT OF L-ARGININE IN REGENERATED ENDOTHELIAL-CELLS

1 We examined regeneration of endothelial cells (ECs), neointima forma tion, decreased endothelium-dependent relaxation (EDR) and changes in the contents of L-arginine, N-G-monomethyl-L-arginine (L-NMMA), asymme trical N-G, N-G-dimethylarginine (ADMA) and symmetrical N-G,N'(G)-dime thylarginine (SDMA) in the regnerated ECs, 6 weeks after balloon denud ation of the rabbit carotid artery. 2 Regeneration of ECs was complete d in 6 weeks and a significant neointima formation accompanied by the decreased EDR was observed. 3 L-NMMA and ADMA contents in the regenera ted ECs (23.5+/-4.3 and 21.2+/-2.0 pmol mg(-1) DNA, respectively) were significantly (P < 0.05 and P < 0.01) higher than those in the contro l ECs (8.8 +/- 3.0 and 7.4 +/- 1.9 pmol mg(-1) DNA, respectively), whe reas L-arginine was significantly (P < 0.005) decreased in the regener ated ECs (31,470 +/- 1,050 pmol mg(-1) DNA) as compared to that in the control ECs (47,870 +/- 1,890 pmol mg(-1) DNA). SDMA content was belo w the assay limits. 4 L-NMMA and ADMA, but not SDMA, inhibited the EDR induced by acetylcholine in a concentration-dependent manner. The inh ibition with L-NMMA and ADMA was prevented by an addition of L-arginin e, but not by D-arginine. 5 These results suggest that the accumulatio n of endogenous inhibitors for nitric oxide synthesis and decreased L- arginine content are associated with decreased NO production/release f rom regenerated ECs and neointima formation.