A pilot study on the effect of radiation on calmodulin in rat submandibular salivary glands

Xerostomia and loss of salivary gland secretion is one of the most common complications of the radiation treatment of head-and-neck malignancies. The secretory mechanism in the salivary glands can be modulated by the concentration of intracellular Ca²⁺. Calmodulin is a calcium- binding protein that is widely distributed in nature and is involved in regulating intracellular calcium. In this study the effect of radiation on the concentration of calmodulin in rat salivary glands was investigated. Fourteen rats were divided into three groups: R1 (n = 4) and R2 (n = 5) received a single dose of 15 Gy and group C (n = 5) received no radiation. R1 and R2 animals were killed at weeks 2 and 10 post-irradiation, respectively. The submandibular glands were removed, homogenized and their total calmodulin was determined. The mean calmodulin concentrations were 6.4 ± 1.1 μg/gland for controls, 14.1 ± 3.7 μg/gland for R1 and 68.2 ± 14.4 μg/gland for R2. Kruskal-Wallis ANOVA revealed a significant increase in the concentration of calmodulin following irradiation (p = 0.003). The relationship between this increase and the loss of salivary gland function is not yet clear.