"Sensing, transfer and regulation of ions and gases: Studies in a model organism, the zebrafish (Danio rerio)"

点击翻译按钮获取中文摘要

This research proposal focuses on two key aspects of fundamental importance to the adaptation of fish to fluctuating environments; regulating the ionic composition of their body fluids and the sensing and transfer of the respiratory gases O2 and CO2. While we have learned much about the mechanisms of ion movement across epithelial such as gills and skin, virtually nothing is know about the metabolic cost of ion regulation - what does it cost (in energy) to move ions across a cell? I will examine this question using ionic uptake by the epidermal ion-transporting cells of zebrafish larvae as a model system. My trainees and I will use state-of-the-art scanning polarographic- and canning ion-selective electrode techniques to simultaneously measure ion and O2 fluxes into ionocytes to provide the first direct estimates of the metabolic cost of ion regulation. Additional research in the field of ion regulation will concentrate on establishing the regulatory mechanisms allowing fish to adjust ion uptake rates during environmental challenges such as lowered ambient O2 (hypoxia) and changing salinity. The basic mechanisms underlying the transfer of O2 and CO2 across biological membranes are being re-evaluated with the discovery of gas channels. The proposed research will exploit the power of "gene knockdown" in zebrafish to examine the possibility that CO2 moves through aquaporins, traditionally thought to function as water channels and that O2 moves though either aquaporins or Rh proteins (ammonia channels). The rate of transfer of O2 and CO2 across respiratory surfaces is governed by their sensing by specialized chemoreceptors. Little is known, however, about the mechanisms of chemoreception in fish. This proposal will focus on the role of carbonic anhydrase in CO2 chemoreception and hydrogen sulphide in O2 chemoreception.