Regeneration of parotid acinar cells after high radiation doses. A morphological study in rat.

The acute and late effects of fractionated irradiation on rat parotid gland acinar cells were studied by light and electron microscopy. At 10 days after the last irradiation session (6 Gy or 9 Gy daily during five consecutive days) no effects were seen. At 180 days, minor loss of acini was detectable after a total dose of 30 Gy. After 45 Gy a massive acinar loss was seen at that time; the number of acini had diminished and minor duct-like structures and scattered amounts of fibrous stroma dominated the slides. The remaining acini were disorganized and usually larger compared with the control side and to non-irradiated animals. The acinar cells appeared larger than in the controls. The ducts were better preserved but the intercalated ducts often seemed to be larger than normal. We suggest that this phenomenon indicates a remaining capacity of the parotid gland to regenerate acinar cells even after high radiation doses.