The effect of γ-irradiation at a dose of 1 Gy on the adenylate- and guanylate cyclase systems of rat platelets at different times of the post-radiation period

Abstract

Objective. To study the effect of total γ-irradiation of the organism of rats at a dose of 1 Gy on the adenylate- and guanylate cyclase systems and their relationship with Ca2+ levels in the platelet cytoplasm.Materials and methods. The studies were carried out on outbred white male rats of mature age (6-7 months) weighing 250±30 g. Animals were irradiated (once and evenly) on the IGUR unit with 137Сs γ-quanta at a dose of 1 Gy (dose rate 0.62 Gy/min, for 1.61 min). Animals of the corresponding age served as controls. To determine the content of cyclic nucleotides, RIO cAMP/cGMP-iodine125-M-IBOX reagent kits were used. The amount of calcium in platelets was determined using a Fura-2/AM fluorescent probe using spectrofluorimeter SM 2203 “SOLAR” (Minsk, Belarus).Results. In the short period after irradiation, an increase in the activity of the adenylate cyclase system is observed. The cAMP level rises 1.8-1.5 times during 3-30 days of the post-radiation period. However, the increase in [Ca2+]cyt on the 3rd day after irradiation leads to its predominance by 1.8 times in relation to cAMP, which explains the appearance of an increased aggregation activity of the blood platelets in the immediate post-radiation period. An increase in the activity of the guanylate cyclase system and an increase in the intracellular content of cGMP are observed on the 90th day, which leads to a decrease in the Ca2+/cGMP ratio by 1.83 times and corresponds to a reduced platelet aggregation activity and the probability of bleeding in the long term of the rehabilitation period.Conclusion. The effects of radiation on the platelets of rats irradiated at a dose of 1 Gy are due to systemic disorders of the main intracellular regulatory mechanisms: Ca2+, cAMP, cGMP. Based on the data obtained, it can be concluded that pharmacological correction in the short-term after irradiation should be aimed at inhibiting the effects of [Ca2+]cyt and adenylate cyclase system activity, and in the long-term, at inhibition of guanylate cyclase system activity.