Predominant periportal expression of the phosphoenolpyruvate carboxykinase and tyrosine aminotransferase genes in rat liver

Abstract

The zonal distribution of phosphoenolpyruvate carboxykinase (PCK) and tyrosine aminotransferase (TAT) mRNA in liver was studied by in situ hybridization with radiolabelled cRNA probes and the abundance of PCK and TAT mRNA was quantified by Northern blot analysis of total RNA with biotinylated cRNA probes. Livers were taken from rats during a normal 12 h day/night rhythm, when they had access to food only during the dark period from 7 pm to 7 am, or during refeeding, when they had access to food after having been starved for 60 h. 1. Daily feeding rhythm: High levels of PCK mRNA were distributed mainly in the periportal and intermediate zone during the fasting period at noon and 6 pm. Feeding caused a rapid decrease in PCK mRNA level and a restriction of PCK mRNA localization to the periportal area within the first 2 h. No further alterations were observed during the following hours of the feeding period. TAT mRNA was distributed also in the periportal and intermediate zone during the fasting period. Feeding first reduced the mRNA level without changing the distribution pattern. Then towards the end of the feeding period TAT mRNA increased again to half-maximal levels and became restricted mainly to the periportal area. 2. Starvation-refeeding cycle: High amounts of PCK mRNA as well as of TAT mRNA were localized predominantly in the periportal and intermediate zone after 60 h of starvation. PCK and TAT mRNA both decreased markedly during the first 2 h of refeeding and then remained almost constant.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatic fibrosis, glomerulosclerosis, and a lipodystrophy-like syndrome in PEPCK-TGF-beta1 transgenic mice.

“…2 B). This regional pattern of distribution is consistent with known sites of PEPCK enzyme activity (28) and with the pattern of expression of reporter transgenes directed by the rat PEPCK 5Ј regulatory sequences (17).…”

Zonation of metabolism and gene expression in liver

“…SDH was demonstrated histochemically (dark precipitates) and PCKmRNA was localized by in situ hybridization using a 35S-labelled antisense RNA (antoradiographic grains). (pp Periportal, pv perivenous) (for details see Bartels et al 1990) 87 interactions. The heterogeneous expression of function and structural proteins may be caused by different rates of transcription, mRNA degradation, translation or protein degradation.…”

A Microfabricated Platform for Generating Physiologically-Relevant Hepatocyte Zonation

“…The importance of recapitulating this hepatocyte metabolic heterogeneity in vitro to create more physiological liver models has been acknowledged for at least 20 years7. Zone 1 hepatocytes are efficient at glucose release from glycogen stores and pyruvate during the post-absorptive phase8910, urea formation from ammonia and amino acid breakdown1011, cholesterol biosynthesis12, and phase II conjugation of xenobiotics into polar entities for excretion13141516. Zone 3 hepatocytes are efficient at glucose uptake and storage as glycogen1017, glutamine formation from ammonia101118, alcohol degradation19, and phase I drug conjugation of xenobiotic compounds via cytochrome P450 monooxygenases142021222324.…”