Osmotic and metabolic responses to dehydration and urea-loading in a dormant,terrestrially hibernating frog |
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Authors: | Timothy J Muir Jon P Costanzo Jr" target="_blank">Richard E LeeJr |
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Institution: | (1) Department of Zoology, Miami University, Oxford, OH 45056, USA |
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Abstract: | Physiological responses to dehydration in amphibians are reasonably well documented, although little work has addressed this
problem in hibernating animals. We investigated osmotic and metabolic responses to experimental manipulation of hydration
state in the wood frog (Rana sylvatica), a terrestrial hibernator that encounters low environmental water potential during autumn and winter. In winter-conditioned
frogs, plasma osmolality varied inversely with body water content (range 69–79%, fresh mass) primarily due to increases in
sodium and chloride concentrations, as well as accumulation of glucose and urea. Decreased hydration was accompanied by a
marked reduction in the resting rate of oxygen consumption, which was inversely correlated with plasma osmolality and urea
concentration. In a separate experiment, resting rates of oxygen consumption in fully hydrated frogs receiving injections
of saline or saline containing urea did not differ initially; however, upon dehydration, metabolic rates decreased sooner
in the urea-loaded frogs than in control frogs. Our findings suggest an important role for urea, acting in concert with dehydration,
in the metabolic regulation and energy conservation of hibernating R. sylvatica. |
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Keywords: | Metabolism Urea Dehydration Hibernation Rana sylvatica |
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