Development of the heterogeneous distribution of carbamoyl-phosphate synthetase (ammonia) in rat-liver parenchyma during postnatal development.

Abstract

Carbamoyl-phosphate synthetase (ammonia) is homogeneously distributed in rat-liver parenchyma at birth, as demonstrated by immunohistochemistry. A heterogeneous distribution can first be demonstrated at 6 days post parturn, but can be masked by use of a too sensitive detection system. This heterogeneity is established by a decrease in enzyme content around the hepatic venules and a considerable increase in enzyme content in the remaining parenchyma.

Distribution of glutamine synthetase and carbamoyl-phosphate synthetase I in vertebrate liver.

“…3 A and D) is very much in contrast to its narrow zonation in mammalian liver. Its distribution in avian liver is, nevertheless, similar to the distribution of its physiological counterpart, CPS-I, in mammalian liver (9,10,12). At higher magnifications, differences in the subcellular localization of GS in liver of the two classes become obvious from the staining pattern: it is punctate in birds, reflecting its mitochondrial localization, and diffuse in mammals, reflecting its cytosolic localization (data not shown).…”

“…CPS-I is found in all hepatocytes with the exception of those in a narrow zone surrounding the terminal hepatic venules. It is to these cells, from which CPS-I is excluded, that GS is exclusively zoned in adult liver (8)(9)(10)(11)(12). Retrograde perfusion of the intact liver results in increased glutamine synthesis, and the zonation of GS to the hepatic venules is considered to be a "fail-safe" mechanism for ammonia detoxification in mammals (13).…”

The Far-upstream Enhancer of the Carbamoyl-phosphate Synthetase I Gene Is Responsible for the Tissue Specificity and Hormone Inducibility of Its Expression

“…Expression is initially found in a few hepatocytes only, but toward the end of the fetal period all hepatocytes have been recruited to express CPS (1-3). After birth, the expression gradually becomes confined to the hepatocytes surrounding the portal veins (3,4). The only other cells producing appreciable levels of CPS mRNA and protein are the enterocytes of the small intestine (3,5).…”

Both Humoral Mesenchymal Factors and the Close Association between the Hepatic Endoderm and Mesenchyme can be Involved in Liver Formation of Mouse Embryos

“…Expression of AFP, albumin and CPSI was examined immunohistochemically. Dewaxed sections were incubated with the normal goat serum (Rockland, Gilbersville, PA, USA)(1/20 dilution with phosphate-buffered saline [PBS] containing 1% bovine serum albumin [BSA]) for 20 min, and then with rabbit anti-mouse AFP antiserum (ICN Biomedicals, Inc., Aurora, OH, USA) (1/50 dilution in PBS-1% BSA), anti-mouse albumin antiserum (Cappel Research Products, Durham, NC, USA) (1/50 dilution), or anti-rat CPSI antiserum (a generous gift from Dr. W. H. Lamers) (Gaasbeek Janzen et al, 1985) (1/1000 dilution) for 1 hr at room temperature. After being thoroughly washed in PBS, sections were then incubated with FITC-labeled goat anti-rabbit IgG antibodies (Cappel Research Products)(1/100 dilution in PBS-1% BSA) for 1 hr at room temperature.…”