Toxicity to non-tumor derived tissues is a significant obstacle in the use of ionizing radiation for cancer treatment. Treatment of head and neck malignancies often includes the salivary glands in the radiation field. Radiation causes an irreversible loss of salivary gland function leading to dry mouth (xerostomia) and to oral malfunctions, speech and food handling difficulties. To date no effective treatment or prevention of this irradiation side effect is available. We mimicked inherent long term adaptive responses to stress (heat) and overexpressed protective gene products by heat acclimation(HA), prior to radiation. These protective gene products include Heat Shock Proteins (HSP) which have the ability to confer protection to one stress via exposure to another (cross tolerance) and are known to increase during HA. The aims of the initial stage of our project were to determine 1) physiological levels of HSP 70 in rat salivary gland tissues; 2) the effects of HA on HSP 70 levels in these tissues; 3) the protective effects of HA prior to ionizing radiation; 4) long term effects of HA on saliva output. Other investigations of the specific role of HSP70 in radioprotecion will be performed using an adenoviral vector encoding HSP70 in a salivary gland cell line and then in vivo. The animal model chosen was the rat, with known normal salivary gland function and that following radiation, and extensively studied in HA research. HA involved continuous exposure to ambient heat, in a climatic chamber at 34 +/- 1oC, 30-40% relative humidity with food and water ad lib for 30 days. Upon removal from the climatic chamber, the head and neck area of the experimental group of rats was irradiated with a single dose of 1500 Rads. Levels of HSP70 in gland tissues were determined using Western immunoblotting. Salivary gland function was determined by saliva output. Salivation was stimulated in anaesthetized rats via subcutaneous pilocarpine injection, saliva was collected from cannulated ducts for 30 minutes. Results show HSP70 increased by 52% in the submandibular tissues and by 28% in the parotid tissues following HA. In the submandibular gland a 50%, 52.3% and 54% decrease in saliva was noted 4,6 and 8 weeks post irradiation respectively, in the animals that underwent HA prior to radiation the decrease in salivation was reduced to 36%, 15%, 21% for the same time periods .In the parotid gland irradiation caused a 41.4% and 68% decrease in saliva flow measured 4 and 8 weeks post irradiation, HA prior to irradiation preserved gland function, with only a 7.8% and 44% decrease in saliva output respectively. No significant differences were noted in the amount of saliva collected in the heat acclimated group compared to the control group (p>0.1) one month after acclimation. We found that heat acclimation(HA) increases levels of HSP70 in salivary gland tissues. No long term effects on salivation were detected following HA. Our results confirm the cross tolerance phenomena between HA and irradiation in salivary glands, with gland function preserved following HA prior to irradiation.