REGULATION OF BILE FORMATION IN RABBITS AND GUINEA PIGS

Despite interruption of the enterohepatic circulation of bile salts, bile flow in conscious rabbits and guinea pigs remained constant for several hours when saline was infused to compensate for loss of water and electrolytes in bile. Thus it appeared that biliary flow in these species is not as highly dependent on bile salt secretion as it is in dogs and man. The effects of other stimulants known to play an important role in regulating bile formation in other species were tested in rabbits and guinea pigs. Secretin, cholecysto‐kinin‐pancreozymin (CCK‐PZ) and gastrin proved to be ineffective choleretics in rabbits although the doses of these exogenously‐administered hormones were sufficient to significantly increase either pancreatic or gastric secretion. Trivial choleretic responses were recorded after administration of secretin and CCK‐PZ to guinea pigs. Attempts were then made to elicit a choleresis by release of endogenous hormones. Again no changes in bile formation were recorded in rabbits although pancreatic secretion was stimulated. Bile flow in guinea pigs increased slightly, but the degree of duodenal acidification necessary to produce all of these responses to endogenous secretin release was probably unphysiological. Attempts to stimulate the release of endogenous CCK‐PZ by infusing peptone were unsuccessful. It was concluded that if these herbivores do elaborate secretin and CCK‐PZ, the factors responsible for their release may differ from those in other species. The present findings provide further evidence that the control of bile formation in rabbits and guinea pigs differs from that in other species, and it is possible that these differences could be related to the temporal pattern of their eating habits.