REGULATION OF CIRCULATING LEVELS OF THE CRUSTACEAN HYPERGLYCEMIC HORMONE - EVIDENCE FOR A DUAL FEEDBACK-CONTROL SYSTEM

The effects of glutamate, aspartate glycine, proline, alanine, taurine , glycerol, glucose and lactate injections on the haemolymph levels of the crustacean hyperglycemic hormone and/or glucose and lactate in th e shore crab, Carcinus maenas, were investigated. Only glucose and lac tate caused significant changes of hyperglycaemic hormone levels. Gluc ose injections resulted in a drop of both hormone and lactate, while l actate had an opposite effect, i.e. it raised both crustacean hormone and glucose levels. The results suggest that during increases in glyco lytic flux, lactate may cause a release of hormone by a positive feedb ack mechanism. The hormone would then stimulate glycogenolysis, thus i ncreasing glucose availability. If more glucose is released than is me tabolized, excess glucose may leak from the cells and suppress crustac ean hyperglycemic hormone release from the X-organ/sinus gland complex by negative feedback.