Yet despite these events, hibernator bile did not differ from summer squirrel bile in several key characteristics find more such as [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. Of note was that 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. Our results highlight the need to further elucidate ASP2215 nmr cholesterol metabolism during hibernation as well as understand the role of gallbladder contractility in determining bile constituents. Methods Adult golden-mantled ground squirrels (Spermophilus lateralis) were captured during the summer from Southern Nevada and California. Some animals were trapped and killed immediately as a seasonal control (summer active, SA). The remaining squirrels were implanted in October with temperature sensitive radiotelemeters as described previously in order to

allow for precise determination of torpor status [33]. Following recovery from surgery, implanted squirrels were housed in an environmental chamber Selleck AG-881 at 4°C and allowed to hibernate. The body temperature of torpid squirrels was ~5°C. In some cases, torpor

status was tracked through surface temperatures using an infrared thermometer. All animals were killed by CO2 asphyxiation except for the torpid animals. Torpid animals were killed by decapitation because of their low respiratory rates. The entire content of the gallbladder was collected to avoid stratification and the bile was snap frozen in liquid nitrogen and stored at -80°C until use. Bile was obtained from animals killed in the summer (SA), animals killed while torpid (T), and animals killed when euthermic between torpor bouts (interbout-aroused; IBA). An additional group of winter squirrels that failed to hibernate was included (deemed abnormal, AB). We note that these AB animals were implanted with telemeters at PTK6 the same time (October), housed under the same conditions (4°C for more than two months), and sampled at the same time of year (~February) as the other winter squirrels. Animals received humane care according to the criteria outlined in the Guide for the Care and Use of Laboratory Animals (Institute of Laboratory Animal Resources, Washington, D.C., USA). To assess for color variation, bile was photographed. Spectral analyses were also performed by diluting 1 μl of bile in 1 ml of water and scanning with a Shimadzu PharmaSpec Spectrophotometer (Shimadzu Scientific Instruments, Columbia, Maryland, USA) from 260 to 700 nm wavelengths at 0.5 nm resolution. Bile acids were measured using a colorimetric assay.