Effect of irradiation on microvascular endothelial cells of parotid glands in the miniature pig.
OBJECTIVE
To evaluate the effect of irradiation on microvascular endothelial cells in miniature pig parotid glands.


METHODS
A single 25-Gy dose of irradiation (IR) was delivered to parotid glands of 6 miniature pigs. Three other animals served as non-IR controls. Local blood flow rate in glands was measured pre- and post-IR with an ultrasonic Doppler analyzer. Samples of parotid gland tissue were taken at 4 h, 24 h, 1 week, and 2 weeks after IR for microvascular density (MVD) analysis and sphingomyelinase (SMase) assay. Histopathology and immunohistochemical staining (anti-CD31 and anti-AQP1) were used to assess morphological changes. MVD was determined by calculating the number of CD31- or AQP1-stained cells per field. A terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) apoptosis assay was used to detect apoptotic cells. The activity of acid and neutral Mg(2+)-dependent SMase (ASMase and NSMase, respectively) was also assayed.


RESULTS
Local parotid gland blood flow rate decreased rapidly at 4 h post-IR and remained below control levels throughout the 14-day observation period. Parotid MVD also declined from 4 to 24 hours and remained below control levels thereafter. The activity levels of ASMase and NSMase in parotid glands increased rapidly from 4 to 24 h post-IR and then declined gradually. The frequency of detecting apoptotic nuclei in the glands followed similar kinetics.


CONCLUSIONS
Single-dose IR led to a significant reduction of MVD and local blood flow rate, indicating marked damage to microvascular endothelial cells in miniature pig parotid glands. The significant and rapid increases of ASMase and NSMase activity levels may be important in this IR-induced damage.
Xu
Junji
J
Salivary Gland Disease Center and Molecular Laboratory for Gene Therapy, Capital Medical University School of Stomatology, Beijing, PR China.
Yan
Xing
X
Gao
Runtao
R
Mao
Lisha
L
Cotrim
Ana P
AP
Zheng
Changyu
C
Zhang
Chunmei
C
Baum
Bruce J
BJ
Wang
Songlin
S
D000818:Animals; D017209:Apoptosis; D051398:Aquaporin 1 / Q000032:analysis; D015415:Biomarkers / Q000032:analysis / Q000378:metabolism; D042783:Endothelial Cells / Q000528:radiation effects*; D020287:In Situ Nick-End Labeling; D008297:Male; D055806:Microvessels / Q000166:cytology / Q000528:radiation effects*; D010306:Parotid Gland / Q000098:blood supply* / Q000201:enzymology / Q000473:pathology / Q000528:radiation effects; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000032:analysis; D011829:Radiation Dosage; D011833:Radiation Injuries, Experimental / Q000201:enzymology / Q000473:pathology*; D012039:Regional Blood Flow / Q000502:physiology / Q000528:radiation effects; D013108:Sphingomyelin Phosphodiesterase / Q000032:analysis / Q000378:metabolism; D013552:Swine; D013556:Swine, Miniature
D015415:Biomarkers; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D051398:Aquaporin 1; D013108:Sphingomyelin Phosphodiesterase