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Pericentral expression pattern of glucokinase mRNA in the rat liver lobulus
A F Moorman1, P A de Boer, R Charles
1Department of Anatomy and Embryology, University of Amsterdam, The Netherlands.
Abstract:
The spatial distribution of glucokinase mRNA (GK mRNA) in rat liver was studied by in situ hybridization under normal and inducing conditions. GK mRNA was first detectable in the liver parenchyma of neonatal rats of 1.5 days. The density of grains decreases in a central-portal direction. This pattern remains essentially unchanged up to 15 days, after which the adult type of distribution gradually starts to develop, i.e. low density of grains indicating low levels of GK mRNA, in which no gradient of expression could be visualized. Within 2 h after an oral glucose load to starved animals, the GK mRNA expression pattern changed from hardly detectable to a clear gradient with the highest grain density around the terminal central venules. Within 6 h relatively high levels of grains, almost homogeneously distributed across the liver lobule, were observed. Glucocorticosteroid treatment also induced GK mRNA in the pericentral area. It is concluded that the observed induction pattern qualifies GK mRNA as a pericentral mRNA suggesting that the pericentral expression pattern of the protein is primarily regulated at the pretranslational level.
Insights
Glucokinase mRNA spatial distribution in rat liver changes with age and glucose levels. Studies show this gene expression is primarily regulated at the pretranslational level, particularly in the pericentral area.
Area of Science:
- Hepatology
- Molecular Biology
- Gene Expression Analysis
Background:
- Glucokinase (GK) is a key enzyme in glucose metabolism, primarily expressed in the liver.
- Understanding the spatial and temporal regulation of GK mRNA is crucial for comprehending hepatic glucose homeostasis.
Purpose of the Study:
- To investigate the spatial distribution of glucokinase mRNA (GK mRNA) in rat liver under normal physiological and induced conditions.
- To determine the regulatory mechanisms underlying GK mRNA expression patterns.
Main Methods:
- In situ hybridization was employed to visualize and quantify GK mRNA distribution in rat liver tissue.
- Experiments involved neonatal and adult rats under normal feeding, starvation, and after glucose or glucocorticosteroid administration.
Main Results:
- GK mRNA was detectable from 1.5 days of age, with an initial central-portal gradient that shifted to a homogeneous distribution in adults.
- Oral glucose load induced a rapid pericentral GK mRNA expression, peaking within 6 hours.
- Glucocorticosteroid treatment also enhanced GK mRNA in the pericentral region.
Conclusions:
- The spatial expression pattern of GK mRNA in rat liver is dynamic and influenced by age and metabolic state.
- The pericentral induction pattern suggests that GK mRNA regulation is primarily pretranslational, with a specific focus on the pericentral hepatocytes.