Regulation of the expression of aquaporins in hepatocytes from the Hyla chrysoscelis

Abstract

<p>My research is focused on the understanding of integral membrane proteins called aquaporins that permit the flow of water through the lipid bilayer of the freeze-tolerant amphibian Hyla chrysoscelis. These proteins selectively let water in and out of the cell down any existing osmotic gradient, and some aquaporins also facilitate diffusion of some small uncharged solutes. More specifically my research focuses on hepatocytes from the liver and whether or not these aquaporins are expressed in these cells and what stresses regulate their expression. For example, HC-3 is a specific aquaporin that permits the flow of glycerol in order to prevent freezing. Therefore, as the liver plays a critical role in metabolism and synthesis of glycerol, I hypothesized that HC-3 expression would be increased by stimuli likely to be associated with transitions to cold and freezing conditions. Aquaporin expression may be regulated by a variety of factors, including hormones. Arginine Vasotocin (AVT) is the amphibian Anti Diuretic Hormone, analogous to arginine vasopressin in humans. Because freezing is a form of dehydrational stress, we hypothesized that AVT would be associated with the physiology of freezing. We are using an in vitro system-primary cultures of hepatocytes-to study whether HC-3 expression is enhanced by AVT. To test this hypothesis, we have developed the method for isolating and culturing hepatocytes, and for maintaining these cultures for several weeks. Using this system, we can add AVT or other potential stimulants, such as glycerol or sucrose, and observe the responses of the cells. We are examining protein expression using Western immunoblots and immunfluorescence. Functional consequences of protein expression are assessed using osmotic swelling assays. The objective of this research is to use an animal model system to understand the regulation of aquaporin proteins. At the same time, we will come to better understand the physiology of tissue freezing and the factors that contribute to successful cryopreservation.</p><p>This presentation occurred at the Wright State University Campus-Wide Celebration of Research, Scholarship and Creative Activities on April 16, 2010</p>