Inositol-phosphoglycan inhibits calcium oscillations in hepatocytes by reducing calcium entry
A Sanchez-Bueno1, M R Greenwood, I Varela-Nieto
1Department of Human Anatomy and Cell Biology, University of Liverpool, UK. antonio@liverpool.ac.uk
Cell Calcium
|February 1, 1997
Summary
Inositol-phosphoglycan (IPG) inhibits calcium oscillations in liver cells by reducing calcium influx. This mediator of insulin action is crucial for maintaining cellular calcium balance and insulin signaling pathways.
Area of Science:
- Biochemistry
- Cell Biology
- Endocrinology
Background:
- Inositol-phosphoglycan (IPG) is implicated as a mediator of insulin action.
- IPG influences various biochemical processes within cells.
- Insulin signaling involves complex intracellular mechanisms, including calcium oscillations.
Purpose of the Study:
- To investigate the role of IPG in regulating intracellular calcium ([Ca2+]i) oscillations in rat hepatocytes.
- To determine how IPG affects calcium influx and its impact on insulin's action.
- To elucidate the mechanism by which IPG modulates cellular responses.
Main Methods:
- Preparation of IPG from rat liver membranes.
- Perfusion of Fura-2-dextran injected rat hepatocytes with IPG.
- Measurement of [Ca2+]i oscillations induced by phenylephrine or vasopressin.
- Use of an antibody to IPG to assess its inhibitory effects.
- Quantification of cytoplasmic Fura-2 quench rate by extracellular Mn2+ to measure Ca2+ entry.
- Manipulation of extracellular calcium concentrations.
Main Results:
- IPG promptly inhibited phenylephrine- or vasopressin-induced [Ca2+]i oscillations in hepatocytes.
- An antibody to IPG reversed the inhibitory effect of insulin on [Ca2+]i oscillations.
- IPG significantly reduced the rate of Mn2+ quench, indicating abolished Ca2+ influx.
- Increased extracellular calcium reversed the inhibitory effect of IPG on [Ca2+]i oscillations.
Conclusions:
- IPG inhibits hepatocyte calcium oscillations by reducing continuous calcium influx.
- This reduction in calcium influx is essential for sustaining [Ca2+]i oscillations.
- IPG plays a critical role in modulating cellular calcium homeostasis and potentially insulin signaling.
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