Nitrite-induced methemoglobinaemia affects blood ionized and total magnesium level by hydrolysis of plasma adenosine triphosphate in rat

The objective of this study was to evaluate the effects of sodium nitrite (NaNO₂)-induced methemoglobinaemia on plasma ATP (adenosine triphosphate) and corresponding changes of blood-ionized magnesium (iMg ²⁺) as well as total magnesium (tMg²⁺) in a time-dependent manner. This study was performed on male Sprague-Dawley rats to which NaNO ₂ was injected (10 mg/kg i.p.) to induce methemoglobinaemia. Methemoglobin (MetHb) in blood was measured before (0 min.) and after 10, 30, 60 and 120 min. of NaNO₂ injection. At respective time points, the tMg²⁺, blood ions and gases were measured by atomic absorption spectrometry and ion selective electrode, respectively. Haematological parameters were checked by automatic blood cell count, and blood films were observed under light microscope. Plasma ATP was measured by bioluminescence assay using a luminometer, and plasma proteins were measured by an automatic analyser. Blood cell count (RBC, WBC and platelet), haematocrit, and haemoglobin were found to be decreased with the advancement of MetHb concentration. With the gradual increase of MetHb concentration, the plasma ATP decreased and blood iMg²⁺ and plasma tMg²⁺ increased significantly as time passed by in comparison with the pre-drug values. A significant decrease of the ratio of ionized calcium to iMg²⁺, Na⁺ and increase of K⁺ was observed. In conclusion, NaNO₂-induced methemoglobinaemia is a cause of hydrolysis of plasma ATP which is responsible for the increase of blood iMg²⁺ and plasma tMg²⁺ in rats.