Corticotropin and morphine interaction in the regulation of phosphofructokinase activity in rat mammary gland.

The roles of corticotropin and morphine in the regulation of phosphofructokinase (PFK) activity in rat mammary glands were investigated by the administration of corticotropin, morphine and dexamethasone. Corticotropin increased the activity of PFK in the mammary glands of intact and hypophysectomised animals but was without any effect in tissues from ovariectomised and adrenalectomised animals. Morphine administration resulted in a significant decrease in the enzyme's activity in intact animals only. A combined dose of corticotropin and morphine significantly reduced the corticotropin-induced increase in the activity in both intact and hypophysectomised animals. Dexamethasone treatment resulted in a significant increase in the activity in hypophysectomised and ovariectomised plus adrenalectomised animals and morphine was able to reduce the glucocorticoid-induced rise. It is postulated that endogenous opioids might be playing a dual role in the regulation of glycolysis by inhibiting the release of corticotropin and regulating the action of glucocorticoids at the cellular level in the mammary gland.