Early membrane injury in lethally irradiated salivary gland cells

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 hours were studied by light and electron microscopy 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 hours 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 hours after irradiation. However, more than 100 per cent increase in serum amylase level was detected prior to the onset of any significant cell necrosis. As early as two hours following irradiation signs of cell membrane injury were demonstrable in the parotid by electron microscopy and consisted of intracellular oedema, sequestered degenerative cell membranes, and an accumulation of intramitochondrial particles. None of these changes was detectable in the submandibular gland. The implication of membrane injury in the lethal effects of radiation on parotid cells is discussed.