Effects of external g-radiation on adenylate cyclase activity in sheep blood cells

In the mechanisms of action of various adverse factors on mammals a special part is assigned to the regulatory systems. The main regulatory system of cellular metabolism is the cAMP system. Exposure of animals to external g-radiation results in the modification of different biochemical processes in cells. In studying diversified intercellular disorders after irradiation it is, therefore, necessary to assess functioning of the cAMP system and its key enzyme, the adenylate cyclase. Note that the data published on the effect of γ-irradiation are mainly obtained with laboratory animals which are significantly different from farmed animals in the body features, whereas the effect in highly productive animals is of special interest. We studied an influence of γ-irradiation on cAMP in Tsygai sheep for the first time and showed a cAMP modification both in the lymphocytes susceptible to radiation and in the thrombocytes which are relatively resistant. In this paper the data are shown on the basal and prostaglandin E 1 stimulated activity of adenylate cyclase in radiosensitive blood cells of sheep exposed to total external g-radiation at a dose of 4 Gy (LD 50/30) for 15 days. In the intact sheep lymphocytes a basal and E 1 stimulated adenylate cyclase activity was 2.82±0.64 pmol/(min х 10 6 cells) and 2.49±0.43 pmol/(min х 10 6 cells), respectively, and in the thrombocytes it amounted 10.90±1.90 pmol/(min х 10 8 cells) and 15.70±5.70 pmol/(min х 10 8 cells), respectively. From the first day after exposure, changes have been revealed in all activity components of this enzyme in the lymphocytes and thrombocytes of sheep. The lymphocytes showed a 1.7-4.3-fold increase in the basal adenylate cyclase activity on days 1-15 and 1.3-3.8-fold increase in the stimulated activity on days 1-10. In thrombocytes the basal activity of adenylate cyclase increased 2.7 and 3.5 times on days 1 and 7, respectively, and the prostaglandin E 1 stimulated activity of adenylate cyclase grew 6.9 and 5.7 times on days 1 and 7 after exposure, respectively. In all other days the adenylate cyclase activity components of interest didn’t practically differ from the initial level. This suggests that i) modification of adenylate cyclase activity is caused by postradiation alteration of the structural-functional condition of plasma membranes in these blood cells, and ii) in the peripheral blood there is a prevalence of more resistant to radiation damage subpopulation of lymphocytes and thrombocytes with increased adenylate cyclase activity