Immunohistological expresión of human Insulin-Like Growth factor I (hIGF-I) and human Growth Hormone (hGH) in the larvae of the mosquito Culex pipiens. Probable involvement in water and mineral balance.

RONDEROS JORGE; ALEJO C. SCARANO; RICCILLO, F.L.; SANTINI, M.S

Arizona

Simposio; Fourth International Symposium on Molecular Insect Sience; 2002

University of Arizona

Most mosquito larvae develop in small aquatic environments. These habitats undergo sudden changes of salinity concentration due to evaporation. Fast and effective physiological changes are necessary to maintain water and mineral balances adjusted to changes of the environmental conditions.The presence of genes coding for proteins with high homology for several growth factors have been described in insects. 1GF-I and GH are well known vertebrate peptidic hormones. They have a basic role as regulators of cell growth and differentiation. They also have been described as regulators of water and inorganic ions balance in mammals. In the present work we analyze the presence of immunoreactive material against hIGF-1 and hGH antiscra in tissues of the larvae of Culex pipiens L. We detected the presence of immunoreactivity in muscle, nervous system, and fat body, suggesting the presence of molecules with some grade of homology to these vertebrate hormones. In addition, we found positive reactions in Malpighian tubes (microvilli), mid-gut (exocytic vesicles) and hindgut. The presence of immunoreactivity in these tissues suggests an involvement of these peptides in the regulation of diuresis in insects. As a first approach to address this hypothesis, we have used an ELISA to analyze the effect of an osmotic shock on the levels of IGF-I. The immunoreactivity for hIGF-I after exposing C. pipiens larvae for 10 min to distilled water was significantly lower that the levels found in control animals (larvae raised in breed water). Mosquitoes exposed to distilled water for 10 min and then placed in breed water for 90 and 180 min showed a tendency to increment IGF-I levels. In summary, we would like to propose that hIGF-1 and hGll-like molecules might play a role as regulators of water and inorganic, ions balance in mosquito larvae.