Fine structure and function of hepatocytes during development

Kanamura, Shinsuke; Kanai, Kazuo; Watanabe, Jun

doi:10.1002/jemt.1060140204

Cited by 48 publications

(39 citation statements)

References 67 publications

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“…The typical adult pattern of predominantly one cell thickness is not established in the human until about five years of age in the child (Morgan & Hartort 1961;Macsween 1994). During the postnatal period, there are also increases in hepatocyte size, average diameter hepatic lobules and quantity of endoplasmic reticulum (Kanai et al 1986;Kanamura et al 1990;Macsween 1994). Sinusoidal fenestrations increase in density in the early postnatal period, coincident with the establishment of zonation of hepatocellular metabolic activity within the acinus (Barbera-Guillem et al 1986).…”

Section: Hepatic Physiologymentioning

confidence: 99%

Neonatal Hepatic Drug Elimination

Gow

Ghabrial

Smallwood

et al. 2001

Pharmacology & Toxicology

104

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After the transition from in utero to newborn life, the neonate becomes solely reliant upon its own drug clearance processes to metabolise xenobiotics. Whilst most studies of neonatal hepatic drug elimination have focussed upon in vitro expression and activities of drug-metabolising enzymes, the rapid physiological changes in the early neonatal period of life also need to be considered. There are dramatic changes in neonatal liver blood flow and hepatic oxygenation due to the loss of the umbilical blood supply, the increasing portal vein blood flow, and the gradual closure of the ductus venosus shunt during the first week of life. These changes which may well affect the capacity of neonatal hepatic drug metabolism. The hepatic expression of cytochromes P450 1A2, 2C, 2D6, 2E1 and 3A4 develop at different rates in the postnatal period, whilst 3A7 expression diminishes. Hepatic glucuronidation in the human neonate is relatively immature at birth, which contrasts with the considerably more mature neonatal hepatic sulfation activity. Limited in vivo studies show that the human neonate can significantly metabolise xenobiotics but clearance is considerably less compared with the older infant and adult. The neonatal population included in pharmacological studies is highly heterogeneous with respect to age, body weight, ductus venosus closure and disease processes, making it difficult to interpret data arising from human neonatal studies. Studies in the perfused foetal and neonatal sheep liver have demonstrated how the oxidative and conjugative hepatic elimination of drugs by the intact organ is significantly increased during the first week of life, highlighting that future studies will need to consider the profound physiological changes that may influence neonatal hepatic drug elimination shortly after birth.The development of clinical pharmacology has resulted in a more rational approach to drug therapy, as well as a deeper understanding of the factors capable of influencing drug disposition, and hence drug effects. Of these factors, age is of great importance. However, substantial differences in drug disposition not only exist between neonates and adults, but also among premature neonates, term neonates, infants and children.During the last two decades drug disposition in the neonatal period has been studied extensively. A major impetus for these studies seems to have been a series of incidents involving illness or death following the administration of drugs at ratios of dose/body weight innocuous in an adult (Craft et al. 1974;Gershanik et al. 1982). These studies have shown that the transition from neonate to childhood is characterised by the ontogeny of all of the processes of drug absorption, distribution, hepatic metabolism and renal excretion, with the development of hepatic drug metabolism being particularly important.The extent to which the neonatal drug-metabolising en-

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Section: Hepatic Physiologymentioning

confidence: 99%

Neonatal Hepatic Drug Elimination

Gow

Ghabrial

Smallwood

et al. 2001

Pharmacology & Toxicology

104

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“…In the mouse, the canaliculi at birth are present but immature and do not attain an adult appearance until 5 days postpartum. In the rat, the earliest canaliculi appear at 12-16 days of gestation but do not attain a mature ultrastructure until 2 days postpartum (Kanamura et al, 1990, and references therein).…”

Section: Development Of the Bile Canaliculimentioning

confidence: 99%

“…The first apparent signs of canaliculi consist of convoluted facing surfaces on adjacent hepatocytes, which appear to be newly forming microvilli (Gallin and Sanders, 1992;Kanamura et al, 1990). These microvilli are immediately followed by development of junction complexes.…”

Section: Development Of the Bile Canaliculimentioning

confidence: 99%

Development and maintenance of bile canaliculi in vitro and in vivo

Gallin

1997

Microsc. Res. Tech.

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“…In fetal mice and rats, infrequent small canaliculi are present, but do not attain an adult appearance until several days postpartum (17). Bile acid synthesis, turnover, and secretion are sparse in fetal liver, and rapidly increase postnatally (18,19), concomitant with hepatocyte polarization and development of a branched canalicular network.…”

mentioning

confidence: 99%

Bile acid stimulates hepatocyte polarization through a cAMP-Epac-MEK-LKB1-AMPK pathway

Wakabayashi

Lippincott‐Schwartz

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

124

115

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This study describes a unique function of taurocholate in bile canalicular formation involving signaling through a cAMP-Epac-MEK-Rap1-LKB1-AMPK pathway. In rat hepatocyte sandwich cultures, polarization was manifested by sequential progression of bile canaliculi from small structures to a fully branched network. Taurocholate accelerated canalicular network formation and concomitantly increased cAMP, which were prevented by adenyl cyclase inhibitor. The cAMP-dependent PKA inhibitor did not prevent the taurocholate effect. In contrast, activation of Epac, another cAMP downstream kinase, accelerated canalicular network formation similar to the effect of taurocholate. Inhibition of Epac downstream targets, Rap1 and MEK, blocked the taurocholate effect. Taurocholate rapidly activated MEK, LKB1, and AMPK, which were prevented by inhibition of adenyl cyclase or MEK. Our previous study showed that activated-LKB1 and AMPK participate in canalicular network formation. Linkage between bile acid synthesis, hepatocyte polarization, and regulation of energy metabolism is likely important in normal hepatocyte development and disease.primary hepatocytes | occludin | P-glycoprotein H epatocytes, the major epithelial cells in the liver, are polarized. Tight junction proteins, including occludin, claudin, and ZO-1, seal the canalicular lumen, thereby separating apical and basolateral membrane domains and forming the bile canaliculus (1). Polarization is essential for biliary secretion. The mechanisms of polarization are complex and include cytoskeletal, tight junctional, and intracellular trafficking components (2-5). Loss of polarity causes bile secretory failure (cholestasis) and liver damage (6).Bile acids are synthesized from cholesterol in hepatocytes, secreted by ABCB11 (Bsep) into the bile canaliculus, and then mostly absorbed into the enterohepatic circulation (7). The major bile acids in mammals are tauro or glycine conjugates of cholic, deoxycholic, and chenodeoxycholic acids (8). In addition to their traditional function in emulsification of dietary fat (8), recent studies reveal that bile acids function as signaling molecules (9), which increase calcium mobilization (10) and cellular cAMP (9); translocate and activate protein kinase C (11), nuclear farnesoid X receptor (FXR), and pregnane X receptors (PXR) (7, 9); activate PI3K/AKT/glycogen synthase kinase 3 (GSK3) (12); and enhance liver regeneration (13).During embryonic development, early fetal hepatocytes are not polarized (14-16). In fetal mice and rats, infrequent small canaliculi are present, but do not attain an adult appearance until several days postpartum (17). Bile acid synthesis, turnover, and secretion are sparse in fetal liver, and rapidly increase postnatally (18,19), concomitant with hepatocyte polarization and development of a branched canalicular network. Based on these events, we postulated that bile acids may regulate hepatocyte polarization and canalicular formation. Using collagen sandwich cultures of rat primary hepatocytes, we confirmed this hy...

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Fine structure and function of hepatocytes during development

Cited by 48 publications

References 67 publications

Neonatal Hepatic Drug Elimination

Neonatal Hepatic Drug Elimination

Development and maintenance of bile canaliculi in vitro and in vivo

Bile acid stimulates hepatocyte polarization through a cAMP-Epac-MEK-LKB1-AMPK pathway

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