A test of alternate models for increased tissue nitrogen isotope ratios during fasting in hibernating arctic ground squirrels
| Autor: | Diane M. O'Brien, Brian M. Barnes, Trixie N. Lee, C. Loren Buck |
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| Rok vydání: | 2012 |
| Předmět: |
Male
Hibernation medicine.medical_specialty Erythrocytes Anabolism Nitrogen Physiology Aquatic Science Biology Models Biological chemistry.chemical_compound Internal medicine Brown adipose tissue medicine Animals Molecular Biology Ecology Evolution Behavior and Systematics Carbon Isotopes Nitrogen Isotopes Isotope Arctic Regions Catabolism Body Weight Sciuridae Fasting Protein catabolism medicine.anatomical_structure Endocrinology chemistry Organ Specificity Insect Science Lean body mass Urea Regression Analysis Female Animal Science and Zoology |
| Zdroj: | Journal of Experimental Biology. |
| ISSN: | 1477-9145 0022-0949 |
| DOI: | 10.1242/jeb.068528 |
| Popis: | Summary We describe two models explaining the increase in tissue nitrogen isotope ratios (δ15N) that occurs during fasting in animals. The catabolic model posits that protein breakdown selectively removes the lighter isotope of nitrogen (14N) from catabolized tissues, causing an increase in the proportion of heavy nitrogen isotope (15N). The anabolic model posits that protein synthesis during fasting results in elevated δ15N values, as the unreplaced loss of 14N to urea results in a higher proportion of 15N in plasma amino acids used for protein synthesis. We effected a range of lean mass loss in arctic ground squirrels (Urocitellus parryii) fasting during hibernation before collecting organ and muscle tissues for analysis of δ15N values. The catabolic model predicts increased δ15N values in both liver and muscle, since these tissues undergo significant catabolism during hibernation. The anabolic model predicts no change in muscle, but an increase in δ15N values in liver, which has high levels of protein synthesis during euthermic phases of hibernation. We found a significant increase in liver δ15N values and no change in muscle δ15N values with lean mass loss, which supports the anabolic model. Heart, small intestine, and brown adipose tissue also increased in δ15N values, indicating protein synthesis in these organ tissues during hibernation. Urine was 3.8‰ lighter than plasma, and both urine and plasma increased in δ15N values with lean mass loss. This study helps clarify the mechanisms causing δ15N change during nutritional stress, thus increasing its utility for physiological research and reconciling previously contradictory results. |
| Databáze: | OpenAIRE |
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