Decrease in salivary secretion by radiation mediated by nitric oxide and prostaglandins.
OBJECTIVE
In the present work, we evaluated the effect of exposing the submandibular glands (SMG) to radiation, studying different functional parameters such as salivary secretion, nitric oxide (NO) production, reactive oxygen species formation, prostaglandin (PGE) content and apoptosis.


METHODS
We irradiated rats in the head and neck region with a single dose of gamma-ray radiation of 15 Gy. Two hours after radiation, we measured norepinephrine-induced salivary secretion. After that, the SMG were dissected, and in this tissue, we measured the activity of NO synthase (NOS), the PGE content, the amount of reactive oxygen species, apoptotic cells and mitochondrial inducible NOS (iNOS) expression.


RESULTS
We found that radiation decreased salivary secretion when 10 and 30 microg/kg of norepinephrine was administered via the right femoral vein. We observed that iNOS activity was reduced and PGE content increased after radiation in SMG, indicating that NO and PGEs may participate in salivary secretion. The expression of mitochondrial NOS was increased after radiation leading to the formation of large amounts of NO that acts as a proapoptotic signal. In fact, we observed an augmentation in apoptotic cells. In this study, we also observed an increase in lipid peroxidation induced by radiation that may contribute to tissue damage.


CONCLUSIONS
Our results indicate that radiation induced a decrease in salivary secretion and SMG iNOS activity, meanwhile the PGE content, the lipid peroxidation and apoptosis increased in the tissue. These modifications decrease salivary secretion.
de la Cal
Carolina
C
Cátedra de Fisiología, Facultad de Odontología, Universidad de Buenos Aires, Buenos Aires, Argentina.
Lomniczi
Alejandro
A
Mohn
Claudia E
CE
De Laurentiis
Andrea
A
Casal
Mariana
M
Chiarenza
Ana
A
Paz
Dante
D
McCann
Samuel M
SM
Rettori
Valeria
V
Elverdín
Juan Carlos
JC
D000818:Animals; D017209:Apoptosis / Q000502:physiology / Q000528:radiation effects; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000502:physiology / Q000528:radiation effects; D004847:Epithelial Cells / Q000378:metabolism / Q000528:radiation effects; D005260:Female; D006258:Head and Neck Neoplasms / Q000532:radiotherapy; D015227:Lipid Peroxidation / Q000502:physiology / Q000528:radiation effects; D009569:Nitric Oxide / Q000096:biosynthesis / Q000528:radiation effects*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism / Q000528:radiation effects; D018384:Oxidative Stress / Q000502:physiology / Q000528:radiation effects; D011453:Prostaglandins / Q000378:metabolism / Q000528:radiation effects*; D011878:Radiotherapy / Q000009:adverse effects*; D051381:Rats; D012463:Saliva / Q000378:metabolism; D013363:Submandibular Gland / Q000378:metabolism* / Q000503:physiopathology / Q000528:radiation effects*; D014987:Xerostomia / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology*
D011453:Prostaglandins; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II