Endocrine control of glycogen synthesis in crabs

Abstract

1. 1. Eyestalk removal in crabs Hemigrapsus nudus and Cancer magister (intermolt stage) is followed by an increase in the activity of UDPG-Glycogen transglucosylase system (UDPG-GT) in muscle tissue. 2. 2. Injection of eyestalk extract into eyestalkless animals decreases the enzyme activity nearly to normal levels. 3. 3. Net synthesis of glycogen in muscle and hepatopancreas, from either glucose or maltose, is not increased by eyestalk removal or depressed by the eyestalk extract injection. 4. 4. The turnover of glucose in glycogen in muscle and hepatopancreas is increased, as indicated by increased specific activity of the glycogen following injection of C 14 glucose or C 14 maltose, by eyestalk removal. 5. 5. Eyestalk extracts have been fractionated by chromatography on Sephadex and the inhibitory factor localized in a definite fraction. 6. 6. The increased turnover is treturned to normal by the injection of crude eyestalk extract or of the purified fraction containing the transglucosylase inhibitor. 7. 7. Eyestalk removal is followed by a marked decrease in total phosphorylase and an increase in the percentage of “inactive” phosphorylase “ b”, but these changes are not reversed by injection of purified fraction of eyestalk extracts. 8. 8. The purified fraction does not increase blood glucose when injected, but does increase the maltose concentration in the blood. 9. 9. These results support the hypothesis that the inhibitor of UDPG-GT acts as a hormone in the control of glycogen synthesis and suggests the possibility that other factors may also be involved in the control of carbohydrate metabolism.