Prior to administration of pentoxifylline, PLS tumors were distinguished by increased levels of deoxyhemoglobin and reduced levels of oxyhemoglobin compared to that of the normal tissue, leading to reduced oxygenation in the tumor model (Figs. 2 and 3). The blood oxygen saturation level in the tumor was significantly lower than that of the normal tissue (
р<0.01). Both HHb and HbO
2 levels were significantly different in the tumor and normal tissues (
р = 0.01 and
р = 0.03, respectively). These indices demonstrate an impaired balance between the delivery and demand of oxygen in the tumor tissue, in accordance with the special biological features of PLS, and contribute to its low oxygenation level and the presence of vast hypoxic areas [
11]. In normal tissue (marrow and cross-stripe muscle), the total hemoglobin level indicates the level of blood-filling of the tissue, while the oxyhemoglobin level indicates the oxygen supply, and the deoxyhemoglobin level indicates the tissue oxygen consumption [
12,
13]. Thus, in tumor tissue, increased concentration of deoxyhemoglobin may reflect disproportionate oxygen supply and demand, which is typical of an actively proliferating tumor such as PLS.