The tissue content of cyclic AMP in rats after microwave irradiation in vivo

When anesthetized rats were exposed to microwave (power output 1.3 kw, frequency 2,450 MHz), the cyclic AMP phosphodiesterase activity showed a rapid decline in the skeletal muscle, heart, trachea and lung; no activity essentially could be detected after a 30 sec irradiation. Cyclic AMP levels in these tissues also decreased rapidly to constant values within 30 sec. Concentrations of cyclic AMP in the heart, skeletal muscle, trachea and lung measured by the tissue fixation with liquid nitrogen were approximately 3, 3, 4 and 4 times higher than those after microwave irradiation, respectively. The intravenous injection of procaterol (1 mu mol/kg), a beta 2-adrenoceptor agonist, caused a 6-fold increase in the trachea cyclic AMP level when measured after microwave fixation but only a 2-fold increase when measured after liquid nitrogen fixation. It is concluded that rapid tissue fixation by microwave irradiation may provide a useful means for obtaining reliable values of the tissue cyclic AMP content.