Is radiation-induced degranulation of mast cells in salivary glands induced by substance P?
Although DNA is the critical target for the lethal effects of irradiation, the precise mechanisms by which irradiation causes damage in tissues and biological systems is not fully understood. In the present study, the number of mast cells and the expression of the neuropeptide substance P (SP) in salivary glands were examined 10 days after a regimen of irradiation. The irradiation was given as a single dose or 5 consecutive days with daily doses of 7 Gy up to a total dose of 35 Gy. In addition, the number of mast cells and the expression of SP were examined 2 and 24 h after a single dose of 7 Gy. Immunohistochemical staining for 5-hydroxytryptamine (5-HT) and staining with avidin peroxidase and toluidine blue were used to detect mast cells. At examination 2 and 24 h after irradiation treatment, no change in the number of mast cells and the pattern of SP expression was observed. Ten days after irradiation there was a remarkable reduction in the number of mast cells in all the three glands, but there was a marked increase in the number of nerve fibers showing SP-like immunoreactivity in the parenchyme. The results show that early time-dependent alterations in the density of mast cells occur in response to irradiation, and that these changes occur concomitantly with changes in the expression of SP. Since the peripheral nervous system is a main regulator of salivary gland function, it is tempting to speculate that the nervous system interacts with mast cells via SP in modulating irradiation provoked tissue responses in salivary glands.
Aalto
Y
Y
Department of Oncology, Umeå University, Sweden.
Forsgren
S
S
Franzén
L
L
Henriksson
R
R
D000818:Animals; D015550:Cell Degranulation / Q000528:radiation effects*; D005260:Female; D007150:Immunohistochemistry; D008407:Mast Cells / Q000378:metabolism / Q000528:radiation effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012469:Salivary Glands / Q000378:metabolism / Q000528:radiation effects*; D013373:Substance P / Q000502:physiology*
D013373:Substance P