Calcium-Induced Stimulation of Cyclooxygenase in Rabbit Leukocytes and its Modulation by Ultraviolet Radiation.
Ultraviolet radiation induces immunostimulative activity in blood. One of the mechanisms of this phenomenon is a photostimulation of blood cell cyclooxygenase (for example, in leukocytes and platelets). It is not known what are the ways of ultraviolet-induced stimulation of the enzyme. To elucidate this, we studied an action of exogenous Ca(2+) on accumulation of cyclooxygenase-mediated lipid peroxidation products in isolated rabbit leukocytes. It was shown, that Ca(2+) at a relatively high concentration (5 mM) induced time-dependent accumulation of lipid peroxidation products in rabbit leukocyte suspension. This effect of Ca(2+) was sensitive for inhibition by cyclooxygenase blocker aspirin, but not lipid antioxidant ionol (butylated hydroxytoluene, BHT). So, the mechanism of Ca(2+)-induced accumulation of lipid peroxidation products in leukocytes involves activation of cyclooxygenase-mediated peroxidation of unsaturated fatty acids. The middle-wave ultraviolet irradiation of leukocyte suspension before Ca(2+) stimulation of cyclooxygenase potentiated Ca(2+)-induced activation of the enzyme. The increased leukocyte cyclooxygenase sensitivity to Ca(2+) action after ultraviolet irradiation may cause well-known ultraviolet photostimulation of cyclooxygenase in leukocytes. This is of high importance for immunostimulative activity of ultraviolet-irradiated blood.
Anosov
Alexander K.
AK
Russian State Medical University, Moscow, Russia.
Miramedova
Aina G.
AG