Extracellular nucleotides such as adenosine-5'-triphosphate (ATP) and reactive oxygen species are essential local signaling molecules in the kidney. However, measurements of changes in the interstitial concentrations of these substances in response to various stimuli remain hindered due to limitations of existing experimental techniques. The goal of this study was to develop a novel approach suitable for real-time measurements of ATP and H₂O₂ levels in freshly isolated rat kidney. Rats were anesthetized and the kidneys were flushed to clear blood before isolation for consequent perfusion. The perfused kidneys were placed into a bath solution and dual simultaneous amperometric recordings were made with the enzymatic microelectrode biosensors detecting ATP and H₂O₂. It was found that basal levels of H₂O₂ were increased in Dahl salt-sensitive (SS) rats fed a high-salt diet compared with SS and Sprague-Dawley rats fed a low-salt diet and that medulla contained higher levels of H₂O₂ compared with cortex in both strains. In contrast, ATP levels did not change in SS rats when animals were fed a high-salt diet. Importantly, angiotensin II via AT₁ receptor induced rapid release of both ATP and H₂O₂ and this effect was enhanced in SS rats. These results demonstrate that ATP and H₂O₂ are critical in the development of salt-sensitive hypertension and that the current method represents a unique powerful approach for the real-time monitoring of the changes in endogenous substance levels in whole organs.
Keywords: ATP; angiotensin II; biosensors; hydrogen peroxide; purinergic signaling.