Black bear (Ursus americanus) bile composition: seasonal changes.

Gallbladder contents from 8 active and 14 dormant black bears were analyzed for individual bile acids by high-performance liquid chromatography and for cholesterol, phospholipids, sodium, potassium, calcium, magnesium, zinc, iron, and copper. Only three bile acids occurring as taurine conjugates were detected: tauroursodeoxycholate, taurochenodeoxycholate, and taurocholate. The proportion of tauroursodeoxycholate to the sum of the three bile acids decreased. Calcium, cholesterol, phospholipids, magnesium, zinc, and copper concentrations were increased in dormancy. Standardized collection and handling procedures yielded more consistent data than previously available. The decrease in tauroursodeoxycholate and absence of deoxycholate and lithocholate are consistent with our working hypothesis that a marked reduction in metabolic activity of the gut flora is an integral part of the adaptation to metabolic stability of the dormant bear.