ABSTRACT
Nitric oxide (NO), first considered a toxic gas, is accepted as an essential biological messenger involved in several functions, e.g., immune processes, endothelium relaxation, neurotransmission. Since NO is a gaseous and labile compound difficult to measure in tissue biopsies, the great majority of the methods employed to evaluate its concentration in vivo are indirect. In this way, citrulline, nitrites, nitrates, NO synthases (NOS) activity or cyclic guanosine monophosphate are measured as parameters linked to the NO production or efficiency. NO standard solutions are prepared in anaerobic conditions. For this purpose, 40 ml of deionized water are introduced in a gas-proof chamber and bubbled with argon for 30 min. In order to test whether the sensor response in vivo varies according to the known effect of the substances injected, an NO donor or an NOS inhibitor are administered intraperitoneally to the anesthetized rat. For this purpose, OFA male rats are prepared.
