INHIBITION OF SUBSTANCE-P-INDUCED HISTAMINE-RELEASE FROM RAT PERITONEAL MAST-CELLS BY ULTRAVIOLET-LIGHT-B IRRADIATION - DECREASED INTRACELLULAR CALCIUM AS A PARTIAL MECHANISM

Background Ultraviolet light irradiation has been shown to suppress im munological reactions of irradiated individuals, however, less attenti on has been paid to the effects on neurogenic inflammation. Objective We have investigated the effect of ultraviolet light B (UVB) irradiati on on substance P (SP)-induced histamine release from rat mast cells. Methods Rat peritoneal mast cells were treated with UVB irradiation an d challenged by SP. Histamine release from the cells and intracellular calcium concentrations ([Ca2+](i)) in the cells were measured. Result s UVB Irradiation at doses used in the present study did not induce hi stamine release from mast cells. UVB irradiation at doses from 25 to 2 00 mJ/cm(2) inhibited 10(-5) mol/L SP-induced histamine release in a d ose-dependent manner. On the other hand, SP-induced increase of [Ca2+] (i) was inhibited by UVB Irradiation only at doses of 100 and 200 mJ/c m(2). Conclusion These data suggest that UVB irradiation inhibits hist amine release from SP-activated rat peritoneal mast cells partially th rough the suppression of an increase in [Ca2+](i).