Plasma concentration and pituitary content of growth hormone (GH) have been measured by radioimmunoassay in female and male mice under various experimental conditions known to elicit GH secretion in primates. Complete cross reactivity between mouse and rat GH was observed. Both plasma GH concentration and pituitary GH content were higher in male than female mice. None of the procedures employed (except 2-deoxyglucose administration in males but not in females) altered pituitary GH content. The stress of ether and/or bleeding on conscious mice resulted in a prompt fall in plasma GH. Thus the mouse, like the rat, responds to stress by an apparent inhibition of GH secretion in contrast to primates where stress stimulates GH secretion. Insulin-induced hypoglycemia resulted in a fall in plasma GH which was statistically significant in female mice but not in males. Neither arginine nor 2-deoxyglucose injections altered plasma GH levels. Plasma GH was unchanged in mice fasted 24 hr, or in fasted mice injected with glucose 20 min before blood sampling. The failure of fasting, insulin-induced hypoglycemia, or 2-deoxyglucose to evoke GH secretion, or of hyperglycemia to lower plasma levels of GH in mice suggests that glucose is not involved in feedback control of GH in this species. None of the stimuli used, which are known to cause GH secretion in primates, was effective in the mouse; thus, this work emphasizes the species differences in GH secretion and control.
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