A TEMPORAL PROFILE OF THE ENDOCRINE CONTROL OF TRYPSIN SYNTHESIS IN THE YELLOW-FEVER MOSQUITO, AEDES-AEGYPTI

Trypsin synthesis and secretion is induced after the female mosquito t akes a blood meal. Its peak activity has been shown to be proportional to the amount and quality of food uptake. Further regulatory elements , hormones from the brain and the ovary, increase the synthethic rate of trypsin in the midgut by a factor of two. We investigated the tempo ral effect of removing the humoral factors by decapitation and ovariec tomy. Trypsin synthesis was reduced to less than half its normal outpu t when the operations were performed prior, or immediately after the b lood meal. Postponing decapitation resulted in an increased activity. However, the dependence on hormones extended up to 14-16 hrs after a m eal, when maximal synthethic rates are assumed. Similarly, ovariectomy had a prolonged effect on trypsin synthesis. Finally, the lack of hor mones reduced the synthetic capacity of the midgut even when small blo od meals were given. We conclude that for continued efficient trypsin synthesis, humoral stimulation is necessary but is not part of the fee dback mechanism that links the presence of food with the amount of try psin secreted. (C) 1998 Elsevier Science Ltd. All rights reserved.