Endogenous nitrogen oxides and bronchodilator S-nitrosothiols in human airways

Recent discoveries suggesting essential bioactivities of nitric oxide (NO.) in the lung are difficult to reconcile with the established pulmonary cytotoxicity of this common air pollutant. These conflicting observations suggest that metabolic intermediaries may exist in the lung to modulate the bioactivity and toxicity of NO.. We report that S-nitrosothiols (RS-NO), predominantly the adduct with glutathione, are present at nano- to micromolar concentrations in the airways of normal subjects and that their levels vary in different human pathophysiologic states. These endogenous RS-NO are long-lived, potent relaxants of human airways under physiological O2 concentrations. Moreover, RS-NO form in high concentrations upon administration of NO. gas. Nitrite (10-20 microM) is found in airway lining fluid in concentrations linearly proportional to leukocyte counts, suggestive of local NO. metabolism. NO. itself was not detected either free in solution or in complexes with transition metals. These observations may provide insight into the means by which NO. is packaged in biological systems to preserve its bioactivity and limit its potential O2-dependent toxicity and suggest an important role for NO. in regulation of airway luminal homeostasis.

Pyridoxal 5'-phosphate levels in children with sickle cell disease

Pyridoxal 5'-phosphate (PLP), the major coenzyme form of vitamin B6, is known to have antisickling properties in vitro. Recently, low plasma PLP levels were reported in a group of adults with sickle cell anemia. We measured the plasma PLP levels in a group of 55 asymptomatic nontransfused children with sickle cell diseases (SCD) to determine the prevalence of low plasma PLP levels in this population. Comparative studies were made with the measurement of PLP in three other groups serving as controls: Group A (black children, n = 36); Group B (white children, n = 37); and Group C (black adults, n = 13). PLP was measured directly in plasma by a radioenzymatic technique. The results of these comparisons showed that there was no statistically significant difference in plasma PLP of black children with SCD (10.7 +/- 10.0 ng/ml) as compared with black control children (group A, 9.0 +/- 12.3 ng/ml). The low plasma levels PLP in these two groups were significantly lower than that of the plasma PLP of white control children (group B, 15.85 +/- 15.92 ng/ml). This data suggest that a high prevalence of low PLP levels exists in black children seen at Grady Memorial Hospital, both with and without SCD.