Influence of chest gamma-irradiation on cough response in awake guinea pigs

Radiotherapy of tumors in the chest and neck regions may have serious pulmonary side effects. It is well known that inflammation is an essential manifestation of radiation-induced injury. This can heal spontaneously, by specific treatment, or it may progress to more intensive inflammation up to irreversible pulmonary fibrosis. To prevent such complications, it would be useful to have a simple non-invasive and sensitive method for monitoring the course of airway and lung post-irradiation inflammation. This study is devoted to search for such a method. We supposed that cough response intensity (CRI) could be one of the methods, which we are looking for. Guinea pigs (Trik strain, n=32) were used in the study. Animals were divided into two subgroups. Animals of a non-untreated (NT) group (n=14; M=7, F=7) were submitted to sham chest irradiation. The animals of a treated (XRT) group (n=18; M=9, F=9) were exposed to a single dose of gamma rays. Cough was provoked by exposure of animals to citric acid aerosol (CA) in gradually increasing concentrations (0.05-1.6M). CRI testing was performed two days before sham/real chest irradiation, than on 1st, 3rd, 10th, 15th, 21st, and 28th days following the day of irradiation. CRI was quantified in each animal by counting the number of coughs induced by all used concentration of CA. We found a significant increase of CRI in the animals of XRT group on 10th and 21st day compared with the NT animals. An increase of CRI also was found inside the XRT group on the 10th day after irradiation compared with the pre-irradiation value of CRI.