Anatomy and development of the extrahepatic biliary system in mouse and rat: a perspective on the evolutionary loss of the gallbladder

Abstract

The gallbladder is the hepatobiliary organ for storing and secreting bile fluid, and is a synapomorphy of extant vertebrates. However, this organ has been frequently lost in several lineages of birds and mammals, including rodents. Although it is known as the traditional problem, the differences in development between animals with and without gallbladders are not well understood. To address this research gap, we compared the anatomy and development of the hepatobiliary systems in mice (gallbladder is present) and rats (gallbladder is absent). Anatomically, almost all parts of the hepatobiliary system of rats are topographically the same as those of mice, but rats have lost the gallbladder and cystic duct completely. During morphogenesis, the gallbladdercystic duct domain (Gb-Cd domain) and its primordium, the biliary bud, do not develop in the rat. In the early stages, SOX17, a master regulator of gallbladder formation, is positive in the murine biliary bud epithelium, as seen in other vertebrates with a gallbladder, but there is no SOX17-positive domain in the rat hepatobiliary primordia. These findings suggest that the evolutionary loss of the Gb-Cd domain should be translated simply as the absence of a biliary bud at an early stage, which may correlate with alterations in regulatory genes, such as Sox17, in the rat. A SOX17-positive biliary bud is clearly definable as a developmental module that may be involved in the frequent loss of gallbladder in mammals.

Comparative anatomy of the hepatobiliary systems in quail and pigeon, with a perspective for the gallbladder-loss

“…This organ has a unique smooth muscle layer that produces the contractile movement necessary for bile flow and, phylogenetically, is considered an ancestral character of vertebrates [ 31 ]. However, the gallbladder has been independently lost by many therian mammals and birds for unknown reasons [ 9 , 14 , 30 ]. In the case of mammals, a previous study reported that gallbladder loss occurred due to the loss of the gallbladder–cystic duct domain, which corresponds to the biliary bud in the pharyngula embryo [ 14 ].…”

Preclinical dosimetry models and the prediction of clinical doses of novel positron emission tomography radiotracers

“…For this study’s Sprague–Dawley rat model, this modification universally improved the precision of dosimetry models. This is likely due to the fact that, unlike humans, rats have no gallbladder 25 . Consequently, it is important to take into consideration species’ anatomical differences when assessing dosimetry of novel PET radiotracers.…”

Effect of pesticides “Butylcaptax (Russia)” and “Droppa (Russia)” on respiration and oxidative phosphorylation of liver mitochondria of pregnant rats and their embryos

“…The rate of oxygen consumption by mitochondria was measured by the polarographic method on an LP-7 polarograph using a rotating electrode under standard conditions at 25°C. The ADF/0 and DK ratios were expressed according to Chance-Williams [10][11][12][13][14][15]. Succinate and α-ketoglutarate served as oxidation substrates.…”

“…The reducing agent of cytochrome oxidase is cytochrome, located in the intermembrane space. This enzyme combines with oxygen and rapidly reduces oxygen to 2 water molecules [15]. The cytochrome oxidase subunit also interacts with phospholipids of mitochondrial membranes [16].…”

“…The inner membranes of mitochondria are called "conjugate" membranes, since they include enzymes for electron transfer and associated phosphorylation. "Conjugating" membranes are characterized by another feature -a strong dependence of the functioning of enzymes on the integrity of the membrane structure [15].…”