[A possible cause of cancer pain]

Under normal conditions, the pH of the brain and the nervous tissues is independent of the blood glucose concentration in the circulation but constantly lowered to values around 7.0. The latter is due to an 8-9% contribution of aerobic glycolysis to the entire energy metabolism of these tissues. However, this proportion as well as the pH value remain unchanged when the blood glucose increases, because the blood-brain barrier and the blood-nerve barrier, which is formed by the myelin sheaths, prevent an excess glucose penetration. If the blood-nerve barrier is damaged, the glucose transport toward the nerve fibres is markedly increased, followed by increased glycolysis, strong acidification of the affected nervous region and, consequently, generation of pain. The destruction of blood-nerve barriers by the outrageous growth of a tumor and the following pH drop in the nervous tissue might be considered an important cause of cancer pain. As was observed in experiments, there is a correlation between blood glucose level and intensity of pain. Therefore, cancer pain can be relieved by measures that either equalize deviations (peaks) of the blood glucose level or even reduce it as such.