Intravasal peroxynitrite generation causes dysfunction in the isolated perfused rat lung via endothelin.

In septic shock excessive nitric oxide and superoxide are produced, thus generating peroxynitrite. This study investigates whether and how intravasal peroxynitrite causes lung dysfunction. To generate peroxynitrite, isolated and ventilated rat lungs were perfused blood-free in a pressure-constant, recirculating mode with hypoxanthine/xanthine oxidase plus sodium nitroprusside. Airway and vascular resistance, and release of thromboxane A2, prostacyclin, and endothelin-1 were assessed over 200 min. Peroxynitrite generation, as demonstrated by oxidation of the marker 2',7'-dichlorodihydrofluorescein diacetate, caused broncho- and vasoconstriction starting after 100 min. Both reactants alone, i.e., NO. or O2, had no effect. The thromboxane A2/prostaglandin H2 receptor antagonist BM13.177 did not affect peroxynitrite-induced broncho- and vasoconstriction. Combined endothelin(A/B) (ET(A/B)) receptor antagonism (BQ123 plus BQ788) prevented broncho- and vasoconstriction more effectively than the ET(A) receptor antagonist BQ123 alone. In tissue from lungs exposed to peroxynitrite, significantly increased amounts of endothelin-1 were detected. This study identifies endothelin-1 rather than prostanoids as a distal mediator induced by the reaction product of superoxide and nitric oxide, i.e., peroxynitrite. It is concluded that 1) endothelin-1 is a causal mediator of peroxynitrite-induced acute rat lung injury, and 2) peroxynitrite-induced broncho- and vasoconstriction are mediated by both ET(A) and ET(B) receptors.

Polysialylated neural cell adhesion molecule serum levels in normal children.

Serum concentrations of polysialylated neural cell adhesion molecule (PSA-NCAM), a developmentally regulated form of the NCAM, have been recently described to be elevated in children with rhabdomyosarcoma and neuroblastoma, proving PSA-NCAM to be a tumor marker of diagnostic relevance to these malignancies. The present investigation was undertaken to define age-dependent reference intervals in normal children. Serum concentrations of polysialylated NCAM were determined in 366 children aged newborn to 17 y and in 18 adult patients by an immunoluminescence assay using the polysialic acid-specific MAb 735. Serum levels in newborn children were 51.7 kU/L (mean +/- 12.0 kU/L SD), whereas in adult patients they were 9.9 kU/L (mean +/- 3.5 kU/l SD). Assigning the patients to 14 different age groups, a gradual decay of PSA-NCAM serum concentrations was observed, and therefore, mean levels and empirical interpolated percentiles were determined for every age group. Applying specially fitted logistic functions, two different sigmoid graphs were obtained describing the age-dependent decrease of serum PSA-NCAM during the neonatal period and during childhood. The age at which the levels reach half the initial value was located at 3.1 d (mean +/- 2 d SE) and 14 y (mean +/- 1 y SE), respectively. There was no difference between male and female individuals. Repeated measurements revealed variations below 10%. For the first time, our study describes serum levels of PSA-NCAM in children of different age and their gradual decay until adulthood.

18O exchange in suspensions of red blood cells: determination of parameters of mass spectrometer inlet system.

A membrane inlet system to a mass spectrometer (MIMS) allows us to monitor the abundance of 18O in CO2 during the exchange of 18O between HCO3-, dissolved CO2 and H2O that occurs after dissolving 18O-labelled NaHCO3 in aqueous solution. Using a mathematical model we quantitate intracellular carbonic anhydrase activity and membrane permeabilities for HCO3-, CO2 and H2O of isolated cells or intact epithelia added to the solution. For these calculations it was necessary to determine (a) the relation between MS signal and [C18O16O], (b) MIMS response kinetics and (c) CO2 leakage during the experiment. The three parameters were determined by stepwise addition of HCl to HCO3- solution: (a) was found to be linear, (b) response times were 7.5 +/- 2s (10 degrees C), 4.5 +/- 1s (20 degrees C), 3.5 +/- 0.6s (37 degrees C), and (c) CO2 leakage was < 1/1000 s-1.