NITRIC OXIDE SYNTHASES AND SEMICARBAZIDE-SENSITIVE AMINE OXIDASE ACTIVITY IN RAT LIVER AND KIDNEY

Putrescine was used as a substrate of semicarbazide-sensitive amine oxidase (SSAO) in this study. Aminoguanidine (AG), a selective inhibitor of inducible nitric oxide (NO) synthase (iNOS), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), which inhibits soluble guanylate cyclase (sGC), as well as N-omega-Nitro-L-arginine methyl ester hydrochloride (L-NAME) and L-NG-monomethyl arginine (L-NMMA) non-selective inhibitors of NOS, were introduced as pharmacological tools to study the participation of different sources of NO in the regulation of SSAO in the liver and kidney of healthy rats. It was observed that AG, when applied i.p. 4 h before the measurements, significantly decreased SSAO activity in the studied organs. On the other hand, ODQ blocked the effect of AG when both substances were applied together. Higher doses of L-NAME and L-NMMA, similarly to AG, significantly decreased the amount of SSAO-dependent production of hydrogen peroxide (H2O2) in the liver and kidney. It is concluded that iNOS via NO and cGMP increases SSAO activity in the studied organs, while the constitutive isoforms eNOS and nNOS have an insignificant effect on this enzyme.