Split-Dose Sparing of γ-Ray-Induced Pulmonary Endothelial Dysfunction in Rats

• Published in: Radiation research 1988-06, Vol.114 (3), p.627-633
• Main Authors: Ward, William F., Hinz, Joann M., Molteni, Agostino, Chung-hsin Ts'ao
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Biological effects of radiation; Cobalt Radioisotopes; Endothelial cells; Endothelium; Endothelium - enzymology; Endothelium - metabolism; Endothelium - radiation effects; Enzymes; Epoprostenol - metabolism; Fundamental and applied biological sciences. Psychology; Gamma Rays; Ionizing radiations; Irradiation; Lung - enzymology; Lung - metabolism; Lung - radiation effects; Lungs; Male; Peptidyl-Dipeptidase A - metabolism; Plasminogen activators; Plasminogen Activators - metabolism; Radiation damage; Radiation Dosage; Radiation injuries; Rats; Rats, Inbred Strains; Thromboxane A2 - metabolism; Thromboxanes; Tissues, organs and organisms biophysics
• ISSN: 0033-7587; 1938-5404
• DOI: 10.2307/3577133

The purpose of this study was to determine whether radiation-induced pulmonary endothelial dysfunction exhibits split-dose sparing. Rats were sacrificed 2 months after a range of 60 Co γ-ray doses (0-40 Gy) delivered to the right hemithorax in either a single fraction or in two equal fractions separated by 24 h. Pulmonary angiotensin converting enzyme (ACE) activity, plasminogen activator (PLA) activity, and prostacyclin $({\rm PGI}_{2})$ and thromboxane $({\rm TXA}_{2})$ production served as indices of lung endothelial function. There were dose-dependent decreases in ACE and PLA activity and increases in PGI2 and TXA2 production after both single and split-dose exposures. The $D_{2}-D_{1}$ values determined from the two-fraction minus single-fraction isoeffective doses were 3.9 Gy for ACE activity, 7.2 Gy for PLA activity, 4.8 Gy for PGI2 production, and 4.7 Gy for TXA2 production. Thus these data demonstrate that over the present range of radiation doses approximately 4-7 Gy is repairable as subeffective endothelial damage during the 24-h interval between fractions. These values agree with previously published estimates of split-dose sparing in mouse lung based on lethality and breathing rate assays.