Effects of Dexamethasone and Pentobarbital on Plasma Growth Hormone Levels in Rats

In intact gentled female rats, plasma GH levels decreased significantly 30 min after ether stress. Injection of a large dose of dexamethasone (400 µg/100 g) 30 min before, also decreased plasma GH levels. However, the suppressive effect of dexamethasone on plasma GH levels injected 3 h before seemed to be greater than that observed at 30 min. In bilaterally adrenalectomized rats, as in the intact rats, plasma GH levels decreased significantly either in response to ether stimulus or dexamethasone injection 3 h before. Resting plasma GH levels in adrenalectomized rats were lower than those in intact rats. Pentobarbital injection 15 min before in intact rats, not only increased plasma GH levels, but also restored the lowered plasma GH levels resulting from dexamethasone pre-treatment. It was concluded that increased output of adrenocorticoids following ether stress did not play an essential role in the reduction of plasma GH levels.