Meeting Abstract
Cope’s gray treefrog, Dryophytes chrysoscelis, is one of few anurans found in North America that can survive the low temperatures of winter by tolerating freezing of its body fluids. Freezing survival can be achieved, in part, by production and accumulation of cryoprotectants: low molecular weight compounds that minimize the physical, biochemical, and molecular challenges associated with internal ice formation. Dryophytes chrysoscelis not only accumulates glycerol and glucose as cryoprotectants, but has also recently been shown to accumulate urea. While production of glucose in D. chrysoscelis is usually induced by freezing, production of glycerol and urea can be induced by low temperature exposure. Although recent studies suggest a role for hepatic glycogen as a source for cryoprotective glycerol and glucose, the source and mechanism involved in anticipatory accumulation of glycerol and urea is not understood. In this study we determined how cryoprotectant levels and the activity of hepatic glycerol-3-phosphate dehydrogenase, aspartate aminotransferase, and alanine aminotransferase changed in summer, fall, and winter frogs, as well as animals exposed to dehydrating conditions. Our results further elucidate the contribution of carbohydrates and amino acids to the cryoprotectant pool, and the role of acclimatization to the development of freeze tolerance.
