Many polar fishes produce macromolecular antifreezes that act in non-colligative way to prevent freezing. Some arctic fishes in the Smelt and Greenling families use a novel method to avoid freezing. These fishes increase the freezing point depression of their body fluids by producing high concentrations of glycerol in winter. This study will focus on the high glycerol concentrations in arctic fishes and the physiological and biochemical implications they have on water balance, kidney and gill function, and metabolism of energy stores. Conservation of glycerol by the kidney and gills will be investigated by measuring glomerular filtration rate, urine flow, drinking rate and permeability of the gills to glycerol. Because glycerol is present only in winter, seasonal variations in these parameters will be determined. The source and fate of glycerol will be determined with assays of glycogen, lipid and key enzymes using cold- and warm-acclimated fish. Additional studies will be conducted to determine the maximum concentrations of glycerol that occur in cold-acclimated fishes, the environmental conditions that regulate its production, and the occurrence of glycerol in other species. A puzzling characteristic of the smelts is that they have both colligative and non-colligative antifreezes. Further studies will be undertaken to explain why two different antifreezes are needed in these species.
