The effects of hypophysectomy on liver glycogenolytic enzymes and starvation response in goldfish (Carassius auratus L.)

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Abstract
The role of the pituitary gland in goldfish liver carbohydrate metabolism was studied by examining the effects of its removal on the livers of starved animals and on glycogenolytic enzymes.Five weeks starvation after hypophysectomy or sham operation resulted in significantly lower total liver glycogen levels compared with respective fed controls. The larger liver glycogen reserves of starved hypophysectomized fish than fed, sham-operated animals indicate gluconeogenesis is operating to produce glycogen.Glucose-6-phosphatase (EC 3.1.3.9) and glycogen phosphorylase (EC 2.4.1.1) were assayed in liver supernatant fractions from hypophysectomized and sham-operated goldfish. Hypophysectomy resulted in an apparent decline in the activity of glucose-6-phosphatase, but no change in glycogen phosphorylase, compared with sham-operated controls. Reduced glucose-6-phosphatase activity is consistent with lowered glycogenolysis as a cause of liver glycogen accumulation in hypophysectomized goldfish. It is suggested that reduced glycogenolysis could be related to reduced peripheral use of carbohydrate. The possible role of ACTH and glucocorticoids is discussed.