Crustacean hyperglycemic hormone (CHH) and the regulation of carbohydrate metabolism: Current perspectives

1. 1. Even though the crustacean hyperglycemic hormones (CHHs), produced by perikarya in the “medulla terminalis X-organ” and released from the sinus glands, are among the best known crustacean neuropeptides, their physiological role in metabolic regulation is far from clear. 2. 2. Previous experiments with eyestalk extract or partially purified preparations have provided evidence of an activating effect on phosphorylase and an inhibitory one on glycogen synthase. It is likely that CHH has this dual role, but the details remain to be confirmed by experiments with pure hormone, particularly with regard to the effects on the phosphorylase system. 3. 3. There is evidence in the literature that glycolysis in crustacean tissues may be controlled by an eyestalk factor, and recent results suggest that this factor may be CHH. 4. 4. The pentose phosphate pathway has been suggested, about 30 years ago, to be under the control of two eyestalk factors. Until now no significant efforts have been made to identify any of them, one of which may be CHH. 5. 5. Although the main metabolic pathways of carbohydrate metabolism have been demonstrated in crustaceans, very little is known about their operation under altered environmental and/or physiological conditions, and even less about their endocrine control. There is evidence that CHH may have a more prominent, central role in such control than has been assumed thus far.