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First published online May 8, 2007
Journal of Experimental Biology 210, 1786-1797 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.004499

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Characterization of circannual patterns of metabolic recovery from activity in Rana catesbeiana at 15°C

A. M. Petersen^* and T. T. Gleeson

Department of Integrative Physiology University of Colorado, Boulder, CO 80309-0354, USA

View larger version (15K): [in this window] [in a new window]   Fig. 1. The effect of cannulation surgery and repeated blood sampling on plasma lactate and blood pH in Rana catesbeiana. (A) Blood pH and (C) plasma lactate levels following a typical (>2 h) cannulation surgery. Differing letters indicate significant differences between treatments (P<0.05, N=4). (B,D) The effect of repeated blood sampling on blood pH (B) and plasma lactate (D; P>0.05, N=4). Values are means ± s.e.m.

View larger version (14K): [in this window] [in a new window]   Fig. 2. The effect of exercise performed in June and January in Rana catesbeiana on the rate of oxygen consumed (O2; ml O2 g–1 h–1) in summer (black circles) and winter (grey squares) and the rate of carbon dioxide produced (CO2; ml CO2 g–1 h–1) in summer (open circles) and in winter (open squares). Values are means ± s.e.m. Asterisks indicate times at which both O2 and CO2 are significantly different from resting frog (REST) values (P>0.05, unpaired t-test by time, N=6–8). Inset shows 240 min average of O2 in winter and summer post-activity; **significant difference (P<0.05, N=6–8) between identical treatments and gases measured in different seasons.

View larger version (14K): [in this window] [in a new window]   Fig. 3. The effect of exercise on blood (A) pH, (B) lactate and (C) glucose concentrations in Rana catesbeiana at 15°C in June. Closed triangles, resting frogs (REST); closed circles, exercise + 4 h recovery (REC 4); closed squares, immediately post-exercise (PE). Values are means ± s.e.m. *Significant difference from REST values (P<0.05, N=6–8).

View larger version (23K): [in this window] [in a new window]   Fig. 4. (A,B) Tissue lactate (A) and glucose (B) concentrations at rest (REST, dark gray bars), immediately post-exercise (PE, light gray bars), and after 4 h of recovery (REC 4, black bars). Values are means ± s.e.m. *Significant difference from REST (P<0.05, N=6–8). (C,D) Tissue glycogen stores (± s.e.m.) in liver (C) and muscle (D) in Rana catesbeiana in January (white bars) and June (black bars) at rest (REST), immediately post-exercise (PE), and after 4 h of recovery (REC 4).

View larger version (6K): [in this window] [in a new window]   Fig. 5. Percentage (mean ± s.e.m.) of injected labeled lactate that was converted throughout the body to glucose (white bars) or glycogen (black bars) or oxidized (grey bars) over 4 h in either resting (REST) or exercised frogs recovered for 4 h (REC 4) in June. Different letters indicate significantly different metabolic fate of lactate between groups (P<0.05, N=7–8).

View larger version (10K): [in this window] [in a new window]   Fig. 6. Lactate conversion (mean ± s.e.m.) to glucose or glycogen in the liver and muscle over 4 h of resting (REST) or 4 h of recovery after activity (REC 4) in January (white bars) or June (black bars). *Significant difference between seasons (P<0.05, N=7–8).

View larger version (9K): [in this window] [in a new window]   Fig. 7. The effect of season on intracellular glucose concentration in different tissues (gastrocnemius muscle, liver and heart) after acclimation and exercise at 15°C. January tissues had a higher glucose concentration at rest (REST), immediately following exercise (PE), and 4 h after exercise (REC 4). Values are means ± s.e.m. Differing letters denote significant difference between glucose concentrations under identical treatment conditions when the experiment was performed in different months (P<0.05, N=6–8).