The histopathological evaluation of the effectiveness of melatonin as a protectant against acute lung injury induced by radiation therapy in a rat model.
OBJECTIVE
This study presents the histopathological evaluation of the effectiveness of melatonin as a protectant against acute lung injury induced by radiation therapy.


METHODS
Thirty-two Wistar rats were divided into four groups. The rats in Group 1 received melatonin and underwent radiation therapy. The rats in Group 2 received no melatonin and underwent radiation therapy. The rats in Group 3 received melatonin and underwent sham radiation therapy. The rats in Group 4 received no melatonin and underwent sham radiation therapy. Melatonin was administered at a dose of 100 mg/kg using an intraperitoneal injection. Radiation therapy was delivered on a Cobalt-60 unit using a single fraction of 18 Gy through an anterior portal covering the right lung in entirety. The rats underwent euthanasia at 6 weeks following radiation therapy. The lungs were dissected and blinded histopathological evaluation was performed.


RESULTS
Concerning the right lung, a decrease in intra-alveolar edema and intra-alveolar erythrocytes was observed despite an increase in activated macrophages, intra-alveolar fibrosis, hyaline arteriosclerosis and alveolar wall thickness for the rats in Group 1 as compared to the rats in Group 2. Concerning the left lung, a decrease in alveolar neutrophils and intra-alveolar erythrocytes was evident despite an increase in activated macrophages, hyaline arteriosclerosis and alveolar wall thickness for the rats in Group 1 as compared to the rats in Group 2.


CONCLUSIONS
This study puts forward the histopathological evidence regarding the effectiveness of melatonin as a protectant against acute lung injury induced by radiation therapy through restrained inflammation, regrettably at the expense of promoted fibrosis. The effectiveness of melatonin as a protectant against acute lung injury induced by radiation therapy needs to be evaluated further for the unresolved concerns regarding the safety.
Serin
Meltem
M
Department of Radiation Oncology, Inönü University, Faculty of Medicine, Malatya, Turkey.
Gülbaş
Hülya
H
Gürses
Iclal
I
Erkal
Haldun Sükrü
HS
Yücel
Neslihan
N
D000818:Animals; D005720:Gamma Rays; D008168:Lung / Q000187:drug effects* / Q000528:radiation effects; D055370:Lung Injury; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000473:pathology / Q000528:radiation effects; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D011833:Radiation Injuries, Experimental / Q000209:etiology / Q000473:pathology / Q000517:prevention & control*; D011837:Radiation-Protective Agents / Q000494:pharmacology; D011878:Radiotherapy / Q000009:adverse effects; D051381:Rats; D017208:Rats, Wistar; D012128:Respiratory Distress Syndrome / Q000209:etiology / Q000473:pathology / Q000517:prevention & control
D011837:Radiation-Protective Agents; D008550:Melatonin