RESUMO
The carcinogenic compound N-nitrososarcosine (NSAR) is found in foods and tobacco products, and its quantification is of great interest. Although the presence of two stereoisomers, E- and Z-NSAR, is well-known, individual investigation of the isomers has not been reported so far. The present study by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) reveals that (i) the mass spectrometric responses of the isomers differ by a factor of approximately two and (ii) the isomer ratio is unstable in freshly prepared standard solutions. As a consequence, NSAR concentrations determined by LC-ESI-MS/MS are biased if those facts are not taken into account. The method described here overcomes the difficulty of stereospecific response by adjusting the isomer ratio and was applied to 100 tobacco products and fully validated for moist and dry snuff reference materials showing expanded measurement uncertainties of ~20% and limits of quantification of ~20 ng/g.
RESUMO
We investigated long-term and circadian blood-pressure changes in a Fischer-->Lewis rat model of chronic renal allograft rejection. Ten days after allogeneic kidney transplantation, rats were equipped with telemetry transmitters for continuous monitoring of blood pressure. Urine was sampled 24, 96 and 180 days after kidney transplantation for measurement of renal protein loss and excretion of nitric oxide metabolites. Proteinuria increased with time after transplantation, while urinary excretion of nitric oxide metabolites declined. In five of six rats blood pressure remained in the normotensive range, and its 24-h pattern was preserved up to 6 months post-transplantation. One animal showed hypertensive blood pressure and a disturbed 24-h pattern with peak values during the rest period. In the post-mortem analysis this rat showed a hydronephrotic kidney graft. In conclusion, blood pressure and its 24-h pattern are preserved after successful allogeneic kidney transplantation in the rat.