Effects of mucus thickness and goblet cell hyperplasia on microdosimetric quantities characterizing the bronchial epithelium upon radon exposure.

PURPOSE: The most exposed tissue upon radon exposure is the bronchial epithelium where goblet cells serve as responsive and adaptable front-line defenders. They can rapidly produce a vast amount of mucus, and can change in number, in response to airway insults. The objective of the present study is to quantify the effects of mucus discharge and goblet cell hyperplasia on the microscopic dose consequences of macroscopic radon exposures. METHODS: For this purpose, computational models of the bronchial epithelium and alpha-particle transport have been prepared and applied to quantify the hits received and doses absorbed by cell nuclei in case of different mucus thicknesses and goblet cell number. RESULTS AND CONCLUSIONS: Both mucus discharge and induction of goblet cell hyperplasia reduce radiation burden at the cellular level, and as such they both can be considered as radioadaptive responses to radon exposure. As compared to basal cell hyperplasia, goblet cell hyperplasia is more effective in reducing the microscopic dose consequences of a given macroscopic exposure. Such changes in exposure geometry highlight the need for improvements in the application of biokinetic and dosimetry models for incorporated radionuclides as well as the dose and dose rate effectiveness factor.

Alterations in gastric mucus secretion in rhesus monkeys after exposure to ionizing radiation.

The aim of the present study was to evaluate the effect of gamma-irradiation on soluble gastric mucus. Six conscious chair-adapted rhesus monkeys were studied once before and twice after exposure to ionizing irradiation (800 rads). Using a marker (99mTc-DTPA) dilution technique, acidic glycoprotein (AG), neutral glycoprotein (NG), ion, and fluid output were determined during a basal period and after the administration of an 80-ml water load. Irradiation significantly increased the outputs of both AG and NG during the basal period. After the water load, NG output remained elevated but irradiation abolished postload AG output thus inhibiting the normal rise in AG output stimulated by the load. Two days after irradiation NG output had returned to control levels whereas AG output was still suppressed. Sodium and potassium ion outputs were unaltered by irradiation. Chloride and fluid outputs were significantly inhibited on the day of irradiation but had returned to control levels within 3 days. These results indicate that irradiation produces significant changes in both the quantity and nature of the soluble mucus glycoproteins secreted into the gastric juice. It is suggested that these changes may compromise the protective ability of gastric mucus.

Effect of radiolabeled materials on tracheal mucous clearance in beagle dogs.

Studies of tracheal mucous clearance were carried out in 6 beagle dogs using a wide range of instilled activities. The dogs were anesthetized with halothane and then 2 separate 10-microliter droplets were deposited, 1 reference droplet containing 25 muCi of 67Ga on the left side of the carina and 1 containing either 3, 50, 250, 500, or 1,000 muCi 99mTc on the right side of the carina. Simultaneous measurements of the positions of the droplets were made every minute for 25 min using a gamma camera detection system. There were no differences in velocities with increasing 99mTc activity. The movements of labeled (100 muCi) and unlabeled Teflon-bismuth discs were also compared. No significant differences were detected but the labeled discs did have slightly higher velocities.