Bile Secretory Apparatus in the Newborn Dog: Relationship between Structural and Functional Immaturities

Abstract

In the dog, bile secretion is not fully mature at birth and develops during postnatal life. To try to establish morphologic correlates to the physiologic deficiencies, we examined the ultrastructure of hepatic parenchyma and biliary epithelium in a newborn puppy and in 3 puppies of 1, 3, and 7 days of age. At birth, the hepatocytes contain much glycogen and fat droplets, a small smooth endoplasmic reticulum and Golgi apparatus, rare autophagic vacuoles, and numerous lysosomes. The sinusoidal microvilli are short, and sub-membrane vesicles are few and small. The bile canaliculus is not dilated, but few and short microvilli and no pericanalicular vesicles are seen. The biliary epithelial cells are normal in size, but the luminal surface of the bile ductule has no microvilli and numerous blebs. These morphologic features change with maturation and, by the first week of life, the fine structure of the hepatocytes, bile ductular cells, and biliary passages resemble that observed in the adult liver. These findings provide morphologic support for the concept that, in the dog, the bile secretory apparatus is immature at birth and develops during postnatal life.

Lipase and Pepsin Activities in the Stomach Mucosa of the Suckling Dog

“…The data presented in this study as well as other recently published information [14,25,32,37,38] indicate that the suckling dog may be an excellent model for the study of milk fat digestion in the suckling infant. Similarities between the newborns of these two species include: similar localization and activity levels of gastric lipase in the puppy to those described recently in human infants [32], immature bile-secretory function in the newborns of both dog and human [4,37], presence of bile-salt-stimulated lipase in the milk [8, 11,25], as well as similar fatty-acid composition of milk fat [38,39].…”

“…Similarities between the newborns of these two species include: similar localization and activity levels of gastric lipase in the puppy to those described recently in human infants [32], immature bile-secretory function in the newborns of both dog and human [4,37], presence of bile-salt-stimulated lipase in the milk [8, 11,25], as well as similar fatty-acid composition of milk fat [38,39].…”

Postnatal development of the gastrointestinal system: A species comparison

“…In the dog, the structure of the liver, particularly the structure of liver cells (hepatocytes and bile ductular cells), and the biliary tree and associated passages attain adult characteristics by postnatal week 1 (Tavoloni et al, 1985; Tavoloni and Schaffner, 1989). Specifically, Tavoloni and Schaffner (1989) reported that most structural maturation occurs during the first 3 days after birth, with full maturity of the biliary tree occurring by the end of postnatal week 1.…”

“…In pigs aged 3–6 days, the majority of bile acids that were secreted were conjugated to glycine or taurine (Henning, 1981). In dogs, bile secretory function of the liver is not fully mature at birth but was between 30 and 70% of adult values by postnatal weeks 4–6 (Tavoloni et al, 1985; Tavoloni and Schaffner, 1989). Tavoloni et al (1985) reported that in newborn dogs, canalicular bile flow was decreased compared to adults while ductular bile water reabsorption was virtually absent.…”

“…Canalicular bile flow in animals aged 0–3 days was approximately one‐half that of adult animals (>1 year) but flow in animals ages 7–42 days was similar to that of adults. Water reabsorption via the bile ducts did not occur during the first 3 days after birth; however, by postnatal weeks 4–6, ductular bile water reabsorption had increased to about 50–70% of adult levels (Tavoloni et al, 1985; Tavoloni and Schaffner, 1989). Also, when compared to adult values, bile acid concentration and mean bile output were significantly reduced in dogs (aged 0–42 days) during postnatal development, while bile flow (in the common bile duct) was relatively comparable to that of the adult (Tavoloni et al, 1985).…”