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DIFFERENTIATION OF ENDOPLASMIC RETICULUM IN HEPATOCYTES : I. Glucose-6-Phosphatase Distribution In Situ
A Leskes1, P Siekevitz, G E Palade
1The Rockefeller University, New York 10021.
The Journal of Cell Biology
|October 30, 2009
Summary
Glucose-6-phosphatase activity develops uniformly across the endoplasmic reticulum in rat hepatocytes. This enzyme distribution is consistent within individual cells, even as it appears asynchronously across the cell population during development.
Area of Science:
- Cell Biology
- Biochemistry
- Developmental Biology
Background:
- Glucose-6-phosphatase is a key enzyme in glucose metabolism.
- Endoplasmic reticulum differentiation is crucial for hepatocyte function.
- Understanding enzyme distribution during development provides insights into cellular maturation.
Purpose of the Study:
- To investigate the distribution of glucose-6-phosphatase activity in rat hepatocytes.
- To examine enzyme localization during endoplasmic reticulum differentiation from late gestation to early postnatal life.
Main Methods:
- Electron microscope cytochemistry was employed to visualize enzyme activity.
- Specific techniques were developed for morphological preservation and artifact control.
- Lead phosphate deposition was used to localize glucose-6-phosphatase activity.
Main Results:
- Glucose-6-phosphatase activity was localized to the endoplasmic reticulum and nuclear envelope at all developmental stages.
- Enzyme activity was initially low and present in few hepatocytes before birth, increasing significantly after birth.
- By 24 hours postpartum, both rough and smooth endoplasmic reticulum showed heavy enzyme deposits, with activity exceeding adult levels.
Conclusions:
- Glucose-6-phosphatase develops concurrently within the entire rough endoplasmic reticulum of individual hepatocytes.
- The enzyme appears throughout the smooth endoplasmic reticulum as it forms postnatally.
- The endoplasmic reticulum exhibits a uniform distribution of glucose-6-phosphatase at this level of resolution.
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