ABSTRACT
To assess whether cancer-induced pleurisy is associated with an alteration of nitric oxide (NO)-synthase activity, the levels of nitrate/nitrite (NOx) were measured in blood serum (BS) and pleural effusion (PE) of 35 cancer patients (secondary pleural metastases and mesotheliomas), eight patients with benign lung diseases, and in BS of nine healthy donors. It was found that (1) BS of patients with secondary pleural metastases had an elevated level (P<0.015) of NOx (59.7+/-24.4 microM, n=28) in comparison with control level of BS for healthy donors (43.4+/-13.5 microM, n=9); (2) BS of mesotheliomas (32.1+/-12.2 microM, n=4) had significantly (P<0.05) lower level of NOx compared to BS of benign patients (61.2+/-28.8, n=6); (3) differences in mean levels of NOx in BS and same PE of examined patient groups did not reach statistical significance, excepting sub-group of patients with primary mammary carcinoma; (4) significant interindividual differences of NOx in all groups of patients were revealed; (5) fluids from about 11% of cancer patients contained extremely high levels of NOx over 100 microM; (6) a significant elevation of apparent NOx level in BS and PE of patients with secondary pleural metastases in comparison with those in BS of healthy donors was revealed when the native, i.e. protein-contained, samples were managed with Griess reagent. The results described here, point up the diverse role of NOx in cancer patients. Its role is far from being clear but it seems that NOx acts as a signaling mediator during the formation of pleural metastases and might be considered as a non-specific marker in the corresponding PE. Furthermore, NOx could be used to give rationale of proper application of anticancer drugs affecting diversely NO-synthase activity in cells. Besides, a casual effectiveness of NOx measurements in native samples from cancer patients using Griess reagent needs additional elaboration.
