739 INDIRECT EVIDENCE FOR IMMATURITY OF GALLBLADDER AND BILE DUCTDLAR WATER REABSORPTION IN THE NEWBORN DOG

Abstract

Bile secretion in the dog is immature at birth and develops during postnatal life (Hepatology 2:717). To determine whether the developmental changes in secretory activity are associated with age-related changes in bile composition, electrolyte levels in plasma, gallbladder bile and hepatic bile were measured in anesthetized suckling puppies of 0-3 (n=3), 7-21 (n=5) and 28-42 (n=8) days of age and fed (n=4) and 24-hr fasted (n=4) adult dogs. Plasma concentrations (meq/1) of sodium (140-148), chloride (101-111), and bicarbonate (20-27) were the same in all animals. Gallbladder bile volume (ml/kg) was similar among puppies (0.2-1.7 mean=0.74) and fed adult animals (0.67±0.3), but significantly higher in fasted dogs (1.13±0.3). Gallbladder bile acid content was 65±11, 89±17, 144±27, 146±42, and 318±46 μeq/kg in these respective groups. Gallbladder sodium concentrations increased with age (176±14, 188±17, 217±18, 252±12, and 279±15 meq/1), whereas bicarbonate (43±9, 32±6, 14±7, 11±4 and 6±2 meq/1) and chloride levels (55±16, 33±11, 24±7, 16±7 and 6±2 meq/1) decreased. In spontaneously secreted hepatic bile, sodium levels increased (161±6, 167±8, 184±10, 176±12, and 179±12, meq/1) and chloride decreased (96±5, 87±9, 80±8, 74±9, and 60±14 meq/1) with age. Bicarbonate concentrations were similar in puppies of different ages (23±4, 22±4, and 19±6 meq/1), but higher in adult dogs (38±7 and 32±7 meq/1). Bile acid concentrations in these respective groups were 30±10, 14±4, 19±7, 49±7 and 78±12 meq/1. 14C-erythritol bile-to-plasma ratio also increased with age in the puppies (1.02±0.05, 1.05±0.08 and 1.24±0.11). In adult dogs, the solute ratio was higher in fasted (1.70±0.24) than fed (1.38±0.14) animals. These results support the view that, in the dog, the gallbladder and the biliary epithelium share a common mechanism for water reabsorption (Na-coupled Cl transport), and suggest that such a mechanism is immature at birth and develops during postnatal life.