Revealing the Distribution of Ion Transport Peptide and the Function of its Prospective Second Messengers on the Hindgut of the Adult Mosquito, Aedes aegypti

The insect excretory system includes the Malpighian tubules and hindgut, and plays a vital role in maintaining hydromineral balance of the haemolymph. Unfortunately, ion and water transport mechanisms in the hindgut of insects are not well understood. In the locust, Schistocerca gregaria, Ion Transport Peptide (ITP) was the first characterized antidiuretic factor shown to act on the hindgut. The present study aimed to delineate the function of ITP, and its proposed second messengers, cAMP and cGMP, on the hindgut of the adult mosquito, Aedes aegypti. In order to generate an ITP recombinant peptide, an endocrine-derived cell culture system involving mouse anterior pituitary (AtT-20) cells was used to transiently express A. aegypti ITP (AedaeITP). Wholemount immunohistochemistry of the central nervous system revealed ITP-like immunoreactivity in the brain, thoracic ganglia, and within the abdominal ganglia of adult A. aegypti. Using the scanning ion-selective electrode technique, the influence of recombinant AedaeITP, cAMP, and cGMP on cation transport across the hindgut was investigated. Results indicate that application of cAMP generally promoted sodium ion absorption, while it generally inhibited potassium ion absorption. Conversely, cGMP generally promoted sodium ion secretion.