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The importance of glucose for the freezing tolerence/intolerence of the anuran amphibians Rana catesbeiana and Bufo paracnemis
Steiner, A. A; Petenusci, S. O; Brentegani, L. G; Branco, L. G. S.
Afiliação
  • Steiner, A. A; Universidade de Säo Paulo. Faculdade de Odontologia de Ribeiräo Preto. Departamento de Fisiologia.
  • Petenusci, S. O; Universidade de Säo Paulo. Faculdade de Odontologia de Ribeiräo Preto. Departamento de Fisiologia.
  • Brentegani, L. G; Universidade de Säo Paulo. Faculdade de Odontologia de Ribeiräo Preto. Departamento de Fisiologia.
  • Branco, L. G. S; Universidade de Säo Paulo. Faculdade de Odontologia de Ribeiräo Preto. Departamento de Fisiologia.
Rev. bras. biol ; 60(2): 321-8, May 2000. graf
Artigo em Inglês | LILACS | ID: lil-262065
Biblioteca responsável: BR1.1
RESUMO
Several species of terrestrially hibernating frogs, turtles and inserts have developed mechanisms, such as increased plasma glucose, anti-freeze proteins and antioxidant enzymes that resist to freezing, for survival at subzero temperatures. In the present study, we assessed the importance of glucose to cryoresistance of two anuran amphibians the frog Rana catesbeiana and the toad Bufo paracnemis. Both animals were exposed to -2 degrees Celsius for measurements of plasma glucose levels, liver and muscle glycogen content, haematocrit and red blood cell volume. Frogs survived cold exposure but toads did not. Blood glucose concentration increased from 40.35 + 7.25 to 131.87 + 20.72 mg/dl (P < 0.01) when the frogs were transferred from 20 to -2 degrees Celsius. Glucose accumulation in response to cold exposition in the frogs was accompanied by a decrease (P < 0.05) in liver glycogen content from 3.94 + 0.42 to 1.33 + 0.36 mg/100 mg tissue, indicating that liver carbohydrate reserves were probably the primary carbon source of glucose synthesis whereas muscle carbohydrate seems unimportant. In the toads, the cold-induced hyperglycaemia was less (P < 0.05) pronounced (from 27.25 + 1.14 to 73.72 + 13.50 mg/dl) and no significant change could be measured in liver or muscle glycogen. Cold exposition had no effect on the haematocrit of the frogs but significantly reduced (P < 0.01) the haematocrit of toads from 20.0 + 2.1 per cent to 5.8 + 1.7 per cent due to a decreased red blood cell volume (from 1532 + 63 70 728 + 87 mm3). When toads were injected with glucose, blood glucose increased to levels similar to those of frogs and haematocrit did not change, but this failed to make them cryoresistent. In conclusion, the lack of cold-induced glucose catabolism may not be the only mechanism responsible for the freeze intolerance of Bufo paracnemis, a freeze-intolerant species.
Assuntos
Texto completo: Disponível Coleções: Bases de dados internacionais Base de dados: LILACS Assunto principal: Rana catesbeiana / Bufonidae / Congelamento / Glucose / Aclimatação Limite: Animais Idioma: Inglês Revista: Rev. bras. biol Assunto da revista: Biologia Ano de publicação: 2000 Tipo de documento: Artigo / Documento de projeto
Texto completo: Disponível Coleções: Bases de dados internacionais Base de dados: LILACS Assunto principal: Rana catesbeiana / Bufonidae / Congelamento / Glucose / Aclimatação Limite: Animais Idioma: Inglês Revista: Rev. bras. biol Assunto da revista: Biologia Ano de publicação: 2000 Tipo de documento: Artigo / Documento de projeto
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