Evaluation of Aquaporins ۱ and ۵ Expression in Rat Parotid Glands After Volumetric Modulated Arc Radiotherapy and Use of Low-Level Laser Therapy at Different Times

Abstract Introduction: This experimental study investigated the mRNA expression of aquaporins (AQPs) ۱ and ۵ in the parotid glands of rats irradiated with volumetric modulated arc therapy (VMAT) and subjected to low-level laser therapy (LLLT) at different time points.Methods: The sample consisted of ۳۰ Wistar rats (Rattus norvegicus) divided into the following groups: control, LLLT alone (LG), radiotherapy alone (RG), and experimental groups that received LLLT at ۲۴ hours (early experimental group [EEG], n=۱۲) and ۱۲۰ hours (late experimental group [LEG], n=۱۲) after radiotherapy. VMAT was delivered at a single dose (۱۲ Gy) and LLLT was performed with an aluminium-gallium-arsenide diode laser (۶۶۰ nm, ۱۰۰ mW), spot area of ۰.۰۰۲۸ cm۲, energy of ۲ J/cm۲ applied to ۳ spots in the region corresponding to the right parotid gland, for ۱۰ consecutive days. The right parotid gland was resected and prepared for RNA extraction. The gene expression of AQPs was evaluated by quantitative polymerase chain reaction (qPCR) using specific TaqMan probes, with the HPRT gene as an internal control.Results: The lowest AQP۱ gene expression was ۰.۸۳ (۰.۲۷) with the use of LLLT ۲۴ hours after radiotherapy (EEG), and the highest was ۱.۵۶ (۰.۸۰) with the use of LLLT alone (LG). Likewise, the lowest AQP۵ gene expression was found in the EEG (mean = ۰.۸۸; SD = ۰.۴۹) and the highest in the LG (mean = ۱.۲۹; SD = ۰.۳۳).Conclusion: The use of LLLT after radiotherapy may contribute to the maintenance and an increase of these proteins, even when used at a later time point after radiotherapy. Keywords: Aquaporins Salivary glands Intensity-modulated radiotherapy Low-level light therapy Rats.