Studies on spleen oxygen tension and radioprotection in mice with hypoxia, serotonin, and p-aminopropiophenone.

Abstract

Abstract : Polarographic measurements of the oxygen tension in the spleen and vena cava, as well as radioprotection studies, were carried out in mice forced to breathe an atmosphere of low oxygen (10%, 7%, and 4.6%) or injected with serotonic (90 mg./kg.) or p-aminopropiophenone (30 mg./kg.). The spleen oxygen levels at 10%, 7%, and 4.6% oxygen were 0.36, 0.27, and 0.10 of normal respectively. The dose reduction factors at the corresponding levels were 1.24, 1.73, and 1.96. Serotonin reduced the oxygen tension to 0.53 of normal and a dose reduction factor of 1.77 was obtained. A dose reduction factor of 1.74 was obtained in PAPP-treated mice irradiated 15 minutes after injection and when the oxygen tension level was 0.35 of normal. A dose reduction factor of 2.92 was obtained in serotonin-treated mice irradiated while breathing an atmosphere of 4.6% oxygen. The greatest decline in oxygen tension occurred in these mice when the level in the vena cava declined to 0.06 of normal. If one plots the relative effectiveness of the radiation (y = 1/DRF) versus the relative oxygen tension (x) of the spleen and vena cava for each of the experimental situations, there exists an approximate linear relationship. The results indicate that there is a small amount of protection by both serotonin and PAPP which is independent of hypoxia. This relationship is given as Fiy = 0.42 + 0.60 x, in which the values of Fi are 1.4, 1.2, and 1.12, where i refers respectively to serotonin, sodium nitrite, and PAPP. (Author)