Nitrosylhemoglobin as a potential bioactive storage form of nitric oxide (NO)

This study was conducted to investigate the bioavailability of nitrosylhaemoglobin (HbFe(II)NO) after intravenous (i.v.) infusion of a saturated nitric oxide (NO) solution in an experimental physiological solution. The haemodynamic properties of nitrosylhaemoglobin were also examined and compared with the haemodynamic effects that followed the administration of a NO-donor such as sodium nitroprusside (SNP). 12 Large White pigs were divided into 3 groups of 4 animals each: group I (NO group) - received an infusion of saturated NO solution at a dose of 1632 nmol/kg; group II (SNP group) - received an equimolar concentration of SNP; and group III (control) - received only a saline solution. Insignificant differences were observed in the HbFe(II)NO electron spin resonance (ESR) signal intensity either during or after the saline infusion, whereas the ESR spectra for pigs treated with NO solution presented a clearly detectable composite signal which increased significantly up to TEI and decreased time-dependently after the NO infusion. Nitrites concentration increased significantly only in the NO group. SNP induced an immediate decrease in mean pulmonary and mean systemic arterial pressures and vascular resistances. It was concluded that HbFe(II)NO was a stable bioactive storage form of NO, able to transport this vasoactive mediator distally from the site of administration, and hence potentially able to induce haemodynamic responses through an endocrine mechanism.