Gene expression in derivatives of embryonic foregut during prenatal development of the rat.

Abstract

Proteins characteristic for the adult cellular phenotype, i.e., carbamoylphosphate synthetase (CPS) for liver and small intestine, arginase for liver, glutamate dehydrogenase (GLDH) for pancreas, liver, and small intestine, and amylase for pancreas were studied immunohistochemically in rat embryos and fetuses. At distinct developmental stages, subsets of enzymes appear synchronously in the foregut derivatives, suggesting that gene expression in the different organs is regulated by common factors. In contrast to the long-held opinion that fetal hepatocytes are a homogeneous cell population, it is shown that arginase and CPS are heterogeneously distributed between ED 16 and ED 20. This heterogeneity is related to the vascular architecture of the liver and disappears perinatally as the result of strong stimulation of enzyme synthesis. In addition, an intercellular heterogeneity in CPS content that is not related to the vasculature is observed between ED 14 and ED 20. This "random" heterogeneity reflects temporal differences in the onset of CPS accumulation in individual cells.

Development of the ornithine cycle in rat liver: Zonation of a metabolic pathway

“…In ED 18 rat embryos, the expression of all ornithine cycle mRNAs was homogeneously distributed over the liver lobule. Interhepatocyte differences in the expression of these mRNAs were present, but they were random and not related to the position of the hepatocytes on the portocentral radius of the liver lobule, resembling our previous findings for CPS protein 21 and mRNA. 22 Zonation of mRNA expression first became apparent at ED 20 for OTC, ASS, and ASL (Fig.…”

“…Up to 18 days of development, the expression of ornithine cycle mRNAs in rat liver was low (Fig. 1A-E cellular heterogeneity (compare with Gaasbeek et al 21 and…”

Urea synthesis from ammonia in periportal and pericentral regions of the liver lobule

“…Recent evidence also suggests that intercellular comCorrespondence co R. G. Thurman, Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina, USA-275 14 partmentation also plays an important role in the regulation of urea synthesis [4, 51. Based on the localization of glutamate dehydrogenase in pericentral regions of the liver lobule, Jungermann and Katz suggested that urea synthesis from ammonia occurs predominantly in pericentral areas [5]. However, carbamoyl-phosphate synthetase I, an important ratedetermining enzyme in urea synthesis, was more active in periportal than in pericentral regions of the liver lobule [6].…”

Gender-dependent regulation of glutamate dehydrogenase expression in periportal and pericentral zones of rat liver lobules.

“…Although GDH is a ubiquitous enzyme, its concentration varies markedly, with relatively high concentrations in liver, brain, kidney, and pancreas (Herzfeld, 1972). In the liver of rat and human, GDH is expressed exclusively in hepatocytes and can be detected as soon as the liver diverticulum becomes recognizable at 11 days of embryonic development (Gaasbeek-Janzen et al, 1988). GDH activity increases several-fold during prenatal development and reaches its adult level at 2 weeks after birth (Lamers and Mooren, 1981).…”