CRUSTACEAN HYPERGLYCEMIC HORMONE (CHH) AND THE REGULATION OF CARBOHYDRATE-METABOLISM - CURRENT PERSPECTIVES

1. Even though the crustacean hyperglycemic hormones (CHHs), produced by perikarya in the ''medulla terminalis X-organ'' and released from t he sinus glands, are among the best known crustacean neuropeptides, th eir physiological role in metabolic regulation is far from clear. 2. P revious experiments with eyestalk extract or partially purified prepar ations 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 pho sphorylase system. 3. There is evidence in the literature that glycoly sis in crustacean tissues may be controlled by an eyestalk factor, and recent results suggest that this factor may be CHH. 4. The pentose ph osphate pathway has been suggested, about 30 years ago, to be under th e control of two eyestalk factors. Until now no significant efforts ha ve been made to identify any of them, one of which may be CHH. 5. Alth ough the main metabolic pathways of carbohydrate metabolism have been demonstrated in crustaceans, very little is known about their operatio n under altered environmental and/or physiological conditions, and eve n less about their endocrine control. There is evidence that CHH may h ave a more prominent, central role in such control than has been assum ed thus far.