Histamine prevents functional and morphological alterations of submandibular glands induced by ionising radiation

PURPOSE: Xerostomia is a common, disturbing side-effect among patients treated with radiotherapy for head-and-neck cancer. The aim of the present work was to investigate whether histamine could prevent salivary gland dysfunction and histological alterations exerted by ionising radiation. MATERIALS AND METHODS: Forty-eight rats were divided into four groups. Histamine and histamine-5 Gy groups received a daily subcutaneous histamine injection (0.1 mg/kg) starting 24 h before irradiation. Histamine-5 Gy and untreated-5 Gy groups were irradiated with a single dose of whole-body Cesium-137 irradiation. Control and untreated-5 Gy groups were given daily saline injections. Three days post irradiation metacholine-induced salivary secretion was measured or animals were sacrificed and submandibular gland (SMG) removed, stained and histological characteristics were evaluated. Proliferation and apoptosis markers were studied by immunohistochemistry. RESULTS: Radiation decreased salivary secretion by 40% in comparison to untreated rats, which was associated with loss of SMG mass, alteration of epithelial architecture, partial loss of secretor granular material, diminished proliferation and a remarkable apoptotic response. In contrast, histamine completely reversed the reduced salivation induced by radiation, conserved glandular mass with normal appearance and preserved the structural organisation of secretor granules. Radiation-induced toxicity is prevented by histamine essentially by suppressing apoptosis of ductal and acinar cells, reducing the number of apoptotic cells per field (19.0 ± 3.8 vs. 106.0 ± 12.0 in untreated animals, P < 0.001), and also by preventing the radiation-induced decrease in cell proliferation. CONCLUSIONS: Histamine prevents morphological and functional radiation-induced damage on SMG, representing a potential radioprotector for treatment of patients undergoing radiotherapy for head and neck malignancies.