Short- and long-term functional vs morphometrical salivary effects of irradiation in a rodent model

Irradiation-induced salivary damage which results in severe xerostomia is a well known entity. However, the underlying mechanism of this phenomenon is still considered enigmatic.

We used one of the most studied models, male Wistar rats, and irradiated them to the head and neck region with both a low dose [2.5 Gy] and a high dose [15 Gy] of irradiation. Then we evaluated salivary gland function, weight and morphology of both parotid and submandibular glands in the same animals. Examinations were obtained for the short-term [3 days], long-term [40 days] and extended-term [90 days] time points.

We found that irradiation with 15 Gy, but not 2.5 Gy, profoundly affected all salivary parameters evaluated, the parotid gland to a greater extent. At 40 days post- 15 Gy irradiation, parotid acini tissue was reduced by 35% [p < 0.01], being replaced by fibrovascular stromal tissue. This reduction was accompanied by parotid weight and function reduction of 27% [p < 0.05] and 58% [p < 0.01], respectively. At ninety days post-15 Gy irradiation, the parotid and submandibular functions were reduced by 84% [p < 0.01] and 62% [p < 0.01] respectively, while the gland weights were reduced by 62% [p < 0.01] and 39% [p < 0.01], respectively.

The accumulated data demonstrate the time and dose dependent effects of irradiation on both parotid and submandibular glands. The effects were more profound for the parotid gland and a partial correlation between salivary hypofunction and parenchymal destruction was demonstrated.