The purpose of the present study is to investigate the protective effect of melatonin against early period parotid gland damage, caused by low- and high-dose rate beams in different dose plans, by using experimental rat models. Eighty Sprague Dawley rats were divided into ten randomized groups, each group being different in terms of dose plan and dose rate. Subjects in the control group were given only sodium chloride. Subjects in the melatonin-only group received 10 mg/kg melatonin. The head and neck region of each rat in radiotherapy only and radiotherapy plus melatonin group was irradiated with single dose (SD) and fractional dose (FD) Flattening Filter (FF) and Flattening Filter-Free (FFF) beams. Radiotherapy plus melatonin group subjects were administered 10 mg/kg melatonin 15 min before radiotherapy, radiotherapy only group did not receive melatonin treatment. Ten days after radiotherapy, the parotid gland of rats was examined for histopathological changes and blood samples were collected for biochemical analysis. When radiotherapy only groups and the control group are compared, for both FF, FFF beam modes and single, fractional dose plans, we observed statistically significant difference in histopathology and biochemical parameters due to irradiation. Melatonin administration in radiotherapy plus melatonin groups contributed to conserving these parameters (p < 0.05). In conclusion, melatonin acts as a significant protective agent against early rat parotid gland damage in varying dose plans for both FF and FFF beams. A difference in radiation-induced damage was not observed between FF and FFF beams using in vivo rat model.

本研究的目的是通过使用实验大鼠模型研究褪黑激素对早期腮腺损伤的保护作用，这种损伤是由不同剂量计划的低剂量率和高剂量率光束引起的。八十只 Sprague Dawley 大鼠被分成十个随机组，每组在剂量计划和剂量率方面都不同。对照组中的受试者仅给予氯化钠。仅褪黑激素组的受试者接受 10 mg/kg 的褪黑激素。仅放疗组和放疗加褪黑激素组每只大鼠的头颈部区域分别用单剂量（SD）和分数剂量（FD）扁平滤光器（FF）和扁平无滤光器（FFF）光束照射。放疗加褪黑激素组受试者在放疗前 15 分钟给予 10 mg/kg 褪黑激素，仅放疗组未接受褪黑激素治疗。放疗后10天，检查大鼠腮腺的组织病理学变化并采集血样进行生化分析。当比较仅放疗组和对照组时，对于 FF、FFF 束模式和单次、部分剂量计划，我们观察到由于辐射导致的组织病理学和生化参数的统计学显着差异。放疗中使用褪黑激素加褪黑激素组有助于保持这些参数。在部分剂量计划中，我们观察到由于辐射导致的组织病理学和生化参数的统计学显着差异。放疗中使用褪黑激素加褪黑激素组有助于保持这些参数。在部分剂量计划中，我们观察到由于辐射导致的组织病理学和生化参数的统计学显着差异。放疗中使用褪黑激素加褪黑激素组有助于保持这些参数。p  < 0.05)。总之，在 FF 和 FFF 光束的不同剂量计划中，褪黑激素可作为一种重要的保护剂，防止早期大鼠腮腺损伤。使用体内大鼠模型在 FF 和 FFF 光束之间未观察到辐射诱导的损伤差异。