Effect of ionizing radiation on tissue cyclic AMP and GMP in experimental rats

Adult male Sprague Dawley rats were exposed to whole-body gamma radiation of 4 Gy and 10 Gy and cyclic AMP and GMP of several tissues were studied 4 hours, 24 hours and 72 hours after irradiation. Animals exposed to 4 Gy exhibited initial increase and subsequent decrease of plasma cyclic AMP, while opposite effects were noted in plasma cyclic GMP. Both groups of irradiated rats showed significant decrease of spleen cyclic AMP with variable responses in cyclic GMP. Initial increase with subsequent decrease of liver cyclic AMP was observed in irradiated animals with unaltered cyclic GMP values. It was interesting to note variable responses of myocardial cyclic AMP in both groups of experimental rats with a significant increase in heart cyclic GMP in rats exposed to 10 Gy only. In contrast, myocardial cyclic GMP was significantly decreased in rats exposed to 4 Gy groups.