Ruolo dell'endotelio nel meccanismo di biotrasformazione del sodio nitroprussiato (SNP): studio in vivo ed in vitro

The purpose of this work was to highlight the role of endothelium in the nitric oxide (NO) release mechanism from sodium nitroprusside (SNP), in vivo and in vitro. We infused SNP (1.67 mol/kg i.v for 24 min), an NO donor, in the anesthetized pig. Nitrosylhemoglobin [HbFe(II)NO] was measured by electron spin resonance (ESR) and the hemodynamic effects were studied. An immediate vasodilatation occurred, despite a 17% of SNP biotransformation as [HbFe(II)NO]. Endothelial cell cultures were then co-incubated with increasing doses of SNP and released NO was determined by chemiluminescence. The endothelium metabolized SNP with formation of a stechiometric amount of NO, thus responsible of the vasodilatation. Therefore, SNP relaxant effect is endothelium-dependent. In vivo it is due to the amount of drug that reaches the endothelial monolayer, without generating [HbFe(II)NO], which is not implied in the vascular response.