Meeting Abstract
P1.80 Saturday, Jan. 4 15:30 Smelt Muscle in Winter: The Effects of Urea, Glycerol and Trimethylamine Oxide on Contractile Properties COUGHLIN, DJ*; LONG, GM; GEZZI, NL; Widener Univ., Chester, PA djcoughlin@widener.edu
Rainbow smelt, Osmerus mordax, experience a wide range of temperatures in their native habitat. In response to extremely cold temperatures in the North Atlantic (approaching -2.0oC), smelt express antifreeze proteins, glycerol, trimethylamine oxide (TMAO) and urea to avoid freezing and maintain function. The physiological influence of these osmolytes are not well understood. Urea is known to destabilize proteins when present in large amounts throughout the blood and muscle tissues, while TMAO is thought to counteract the protein-destabilizing forces of urea. Glycerol’s influence on muscle function has not been explored. We examined the effects of urea, glycerol, and TMAO through muscle mechanics experiments with treatments of the three osmolytes at physiologically relevant concentrations. The contractile properties of white muscle bundles were determined in normal saline and in the presence of 50mM urea, 50mM TMAO, and 200mM glycerol in saline. Muscle exposed to urea and glycerol produced less force and displayed slower contractile properties. However, treatment with TMAO led to higher force and faster relaxation by muscle bundles. Preliminary experiments suggest that TMAO also increased power production during cyclical activity. When muscle bundles were exposed to a combination of all three compounds, they displayed no change in contraction kinetics relative to control. The results suggest that maintenance of muscle function in winter smelt requires balanced combination of urea, glycerol and TMAO. The mechanisms of action of these osmolytes, particularly TMAO, will provide insights into muscle function in a variety of fishes that employ these osmolytes for freeze resistance and osmotic balance.
