RESUMEN
Methotrexate is a folate antagonist first developed for the treatment of malignancies and subsequently used in non neoplastic diseases such as rheumatic arthritis, systemic lupus erythematosus, psoriasis and graft-versus-host disease.Apoptosis is a distinct form of cell death and occurs under a variety of physiological and pathological conditions.The current study was done to detect the prevalence of apoptotic cells in the rat submandibular salivary gland after injection of methotrexate using terminal deoxynucleotid transferase-mediated deoxyuridine triphosphatebiotin nick end labeling [TUNEL] method. This method specifically cleaved DNA fragments and chromatin condensations associated with apoptosis, even in formalin fixed paraffin-embedded tissues.Twenty male Albino rats were used in this study, ten rats were used as a control group and were given 2ml saline orally/day for 7 days. The other ten rats were given methotrexate in a dose of 15 mg/kg- body weight/orally for 7 days. [This dose is used usually for treatment of non-neoplastic diseases] At the end of experimental period, all rats were killed and submandibular glands were dissected and processed for histological and immunohistochemical examination. The submandibular glands in methotrexate treated rats showed marked histological alteration and scattered apoptotic cells in the acini as well as the connective tissue stroma