Effect of irradiation on enzyme activities of cyclic AMP system in the neuro- and adenohypophyses.

The enzyme activities of cyclic AMP system in the neuro- and adenohypophyses were studied, immediately after an irradiation by a single whole body exposure of 1600 R, in an attempt to find whether this intervention causes the changes in the responsiveness of the cyclic AMP regulatory system. In the irradiated rats the neurohypophyses revealed a reduced activity of adenylate cyclase, moderately increased activity of phosphodiesterase and slightly decreased activity of protein kinase, including the value stimulated by cyclic AMP. In the adenohypophyses the irradiation did not cause any significant changes in the enzyme activities of the cyclic AMP system, except of slightly decreased adenylate cyclase activity. The possible relationship of the plasma level of antidiuretic hormone immediately after irradiation and the enzyme activities of cyclic AMP system is discussed.