%0 Journal Article
%T Bile constituents in hibernating golden-mantled ground squirrels (Spermophilus lateralis)
%A Julie A Baker
%A Frank van Breukelen
%J Comparative Hepatology
%D 2009
%I BioMed Central
%R 10.1186/1476-5926-8-2
%X Surprisingly, hibernator bile did not differ from summer squirrel bile in key characteristics including [bile acids], [cholesterol], [free fatty acids], [lecithin], and osmolality. One major distinction between summer and winter squirrels was that winter squirrels experience >5 fold increases in [bilirubin]. Such an increase may have significant physiological consequences that could aid in survivorship of torpor. Animals that failed to hibernate, despite being anorexic, were very similar to summer squirrels in all measured parameters except they had lower bile acid and lecithin concentrations.The data indicate that despite extended anorexia, differences in metabolic fuel privation, and bouts of reduced body temperatures, hibernators normally do not experience broad changes in hepatobiliary function.Hibernation is a strategy employed by many different mammals presumably as a means for energy conservation during periods of great thermal stress and limited food resources [1,2]. Ground squirrels of the genus Spermophilus are exemplary hibernators. Their winter seasons are characterized by bouts of torpor wherein body temperature may approach ambient to as low as -2¡ãC [3,4] and metabolic rates may be as low as 1% of the active rate [5]. These torpor bouts may last 1¨C3 weeks and are interrupted by brief (~20¨C24 h) sojourns to body temperatures and metabolic rates typical of an active animal.During the winter, golden-mantled ground squirrels (S. lateralis) are anorexic. Even when housed with free access to food, very few of these animals will eat for the entire ~6 month hibernation season (personal observations). Instead, animals rely on immense fat stores that were gained in an anticipatory period during late summer [2]. Hibernating animals utilize a primarily fat-based metabolism as reflected by a typical respiratory quotient (RQ) of 0.71 but employ a more carbohydrate-based metabolism (RQ = ~0.9) during the interbout-arousal [6]. As expected, the consequences of the ano
%U http://www.comparative-hepatology.com/content/8/1/2