Early Membrane Injury in Lethally Irradiated Salivary Gland Cells

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Abstract
The early manifestations of radiation injury in salivary glands were investigated in the rat. The animals received a single X-ray dose in the range of 200-2000 rad to their neck area. Glandular changes during the first 24 h were studied by light microscopy and EM and by measuring serum amylase activity. The amount of cell necrosis was quantitated and expressed as necrosis index (NI). Parotid NI and serum amylase activity 24 h following irradiation were directly proportional to the X-ray dose. The submandibular gland cells were radioresistant and so were the mucous cells of the sublingual gland. The major increase in parotid acinar cell necrosis occurred between 12 and 24 h after irradiation. More than 100% increase in serum amylase level was detected prior to the onset of any significant cell necrosis. As early as 2 h following irradiation signs of cell membrane injury were demonstrable in the parotid by EM and consisted of intracellular edema, sequestered degenerative cell membranes and an accumulation of intramitochondrial particles. No change was detectable in the submandibular gland. The implication of membrane injury in the lethal effects of radiation on parotid cells is discussed. [Radiotherapy is an effective modality for treatment of cancer of the oral cavity and pharynx. The usually unavoidable damage to normal salivary tissue constitutes a major drawback.].