The endocrine regulation of hydromineral balance in aquatic vertebrates

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As a comparative physiologist/endocrinologist, I am interested in how animals "work". My research program is focused on how the endocrine system regulates salt and water balance in aquatic vertebrates such as fishes. Like all animals, fishes must maintain "homeostasis" (i.e. internal stability). When circulating salt (i.e. ion) levels are out of balance, either through natural alterations in environmental conditions or through environmental disturbance, the endocrine system regulates the reinstatement of homeostasis. This occurs through the action of hormones on tissues that regulate the transfer of water and salt between the animal body and the surrounding environment. These tissues include the kidney, gastrointestinal tract and skin. In fishes, the gills are also particularly important because they directly interface with surrounding water. These aforementioned tissues are referred to as epithelia and they each establish a barrier that separates two fluid compartments. In the case of the gill, these two compartments are the body and the surrounding water. Epithelial tissue regulates the movement of ions and water either across the cells (transcellular) or between the cells (paracellular). While a lot of research has been conducted in order to understand the movement of ions across cells, very little has been done in order to understand what regulates the movement of ions between cells. This is surprising because the permeability of the paracellular route is controlled by the tight junction (TJ) complex and TJs are widely acknowledged to be very important in the general physiology of all vertebrate organisms. My work over the coming grant cycle will focus on gaining a much better understanding of the "machinery" that regulates the permeability of the TJ in fishes and how it is controlled by the endocrine system. With NSERC support I have already demonstrated that some of the proteins that comprise the TJ complex are very sensitive to environmental change and I hypothesize that TJ proteins play an extremely important role in the general well-being of aquatic organisms and ultimately our aquatic ecosystems.