Postnatal development of bile secretory physiology in the dog.

To determine whether bile formation in the dog is an immature process at birth, several determinants of bile secretion were studied in anesthetized, bile duct-cannulated puppies of 0-42 days of age and adult dogs. Basal canalicular bile flow rate, estimated by 14C-erythritol biliary clearance, averaged 0.182 microliter/min/g liver in 0-3 day-old puppies and increased to 0.324 and 0.461 microliter/min/g in puppies 7-21 and 28-42 days of age, respectively. The latter two values were not significantly different from that observed in adult dogs (0.348 microliter/min/g). This age-related increase in canalicular bile flow could be accounted for primarily by an increase in bile acid independent bile flow (0.103, 0.277, 0.375, and 0.252 microliter/min/g in 0-3, 7-21, and 28-42 day-old puppies and adult dogs, respectively). Calculated ductular bile water reabsorption (14C-erythritol biliary clearance-bile flow) was virtually absent in 0-3 day-old puppies (0.005 microliter/min/g), and averaged 0.017 and 0.092 microliter/min/g in puppies of 7-21 and 28-42 days of age, respectively. In adult dogs, ductular bile water reabsorption was 0.132 microliter/min/g. These functional deficiencies of the newborn dog were associated with an increased biliary permeability to 3H-inulin which could not be accounted for solely by an increased solute diffusion due to the lower rate of canalicular bile flow. Administration of taurocholate up to 2000 nmol/min/kg produced in all animals a similar increase in canalicular bile flow and bile acid excretion, and was not associated with changes in ductular bile water reabsorption rate. These findings are interpreted to indicate that, in the dog, bile secretory function is immature at birth and develops during postnatal life.