KAPPER, M.A.; Central Connecticut State University: Modulation of Water Permeability in Gills of Geukensia demissa During High-Salinity Adaptation
During the course of adaptation to altered environmental salinities, estuarine molluscs typically swell or shrink according to the osmotic movement of water down its concentration gradient. These volume changes are eventually reversed by the accumulation or elimination of intracellular solutes during a regulatory phase. Most investigations of volume regulation in estuarine molluscs have concentrated on determining the identity and metabolic sources and fates of intracellular solutes. Little attention has been paid to the regulation of water movement through cell membranes. According to the fluid mosaic model, phospholipid bilayers are impermeant to polar molecules like water. Cell membranes in a number of species have been demonstrated to incorporate specific water-channel proteins (aquaporins) within their structure. Tissues that physiologically regulate their water permeability (such as kidney tubule collecting ducts) accomplish this feat by adding aquaporins to or subtracting aquaporins from their cell membranes. I hypothesize that estuarine mollusce will use a similar procedure to modulate water flux between cells and intercellular spaces during volume regulation. Samples of the ribbed mussel Geukensia demissa were collected from marshes on Long Island sound and adapted to 15o/ooS and 15oC. The presence of aquaporins 1-4 in gill tissue of these low-salinity adapted animals was demonstrated by western dot-blotting using primary antibodies and control antigen from Alomone Laboratories, with colorimetric visualization using HRP-conjugated secondary antibodies and 4-chloronapthol from Bio-Rad. Results from salinity-transfer experiments will be discussed. Supported in part by CSU-AAUP grant ARKAR003 to MAK.
